Lab Final–Assignment Questions

Question 1

Skull: locate the following parts on the Canis latrans skull. Try to remember them and to locate them by heart on the other specimens you’ll encounter during the labs (at least the bigger bones and the foramens):
1) Cranium (braincase + rostral region)
2) Mandible (Lower jaw)
3) Rostrum (upper jaw + bones surrounding the nasal passages and divide these passages from oral cavity)
4) Nasal (bone and passage)
5) Frontals (sit above nasal bones, beside the big cavity)
6) Orbit
7) Parietals (behind the eyes, flanking sagittal crest)
8) Sagittal crest (sticks up on top of skull)
9) Occipital (bone and condyle)
10) Foramen magnum (on underside of skull, hole at base of skull)
11) Auditory bulla (big bulge bone on underside of skull towards base)
12) Premaxilla (underside of skull, bone close to incisors before the little holes)
13) Maxillary (underneath the frontals, sitting beside nasal bones)
14) Infraorbital foramen (little holes near incisors on upper jaw)
15) Zygomatic arches (bones that outline the big holes, one on each side)
16) Jugal (attached to zygomatic arch, lower part of hole towards nose)
17) Squamosal (attached to zygomatic arches on base of skull at upper/back branch)
18) Mandibular fossa
19) Lacrimal (bone + foramen)

Answer 1

Question 2

Qualitatively compare the orbits of Pan troglodytes, Felis catus, Didelphis virginianus, Rattus rattus and Odocoileus virginianus:
- Based on those comparisons, can you tell which ones are mostly prey? Which ones are predators? Why?

Answer 2

The predators are the Felis cats (domestic cat) and the didelphid Virginians (opossum). The prey are Odocoileus Virginians (white-tailed deer), Ratticus ratticus (rat), and Pan troglodytes (chimpanzee).

Predators tend to have forward facing eyesight and large eyes compared to the skull size. Prey tend to have more sideways facing eyes and sometimes smaller eyes compared to the skull size. Chimpanzees are an exception to this.

Question 3

Qualitatively compare the placement of the foramen magnum of Gorilla gorilla, Alces alces, Rattus rattus, Castor canadensis. What does it tell you about the posture of each species?

Answer 3

The foramen magnum is the large opening in the skull through which the spinal cord connects to the brain. Its position relative to the skull can provide insights into the posture and locomotion of a species.

Gorilla gorilla: the foramen magnum is positioned more centrally under the skull compared to quadrupeds, but not as forward as in humans. This reflects their semi-upright posture (from knuckle-walking) and adaptation to both terrestrial and arboreal locomotion.

Alces alces (Moose): the foramen magnum is located toward the back of the skull, which is typical of quadrupeds and indicates a horizontal spine and head that projects forward (quadrupedal locomotion).

Rattus rattus (Black rat): the foramen magnum is positioned centrally but slightly toward the back of the skull, which reflects the hunched over posture of rats that is favourable for omnivorous foraging and climbing behaviours.

Castor canadensis (beaver): the foramen magnum is positioned centrally but slightly posterior (higher up in the back), similar to rats. Because beavers are semi-aquatic quadrupeds with a horizontal body posture, the central placement supports their ability to hold their head upright while swimming or manipulating objects with their forelimbs.

Question 4

Teeth: When you are looking at a specimen, ask yourself what kind of cheek teeth it has. What does it mean about its diet? Hint: Look at both shape and height of the teeth.

Answer 4

Cheek teeth:
There are two types of cheek teeth: tribosphenic and quadritubercular.

Tribosphenic teeth: occur in primitive placental and marsupial mammals
Quadritubercular tooth: addition of the hypocone (hypoconid) to have 4 cusps

Some specialized tribosphenic cheek teeth include: zalambdodont, dilambdodont, euthemorphic (quadrate).

As for specialized quadritubercular teeth:
Herbivores tend to be selenodont or lophodont, which means their teeth are “u” or “w” shaped and adapted for grinding up tough plant material.
Omnivores tend be bunodont, which are square teeth (think human molars).
Carnivores are often secodont; these cheek teeth are higher on the buccal side than the lingual side. Carnivores also have what is called “the carnassial pair”, which is when the fourth upper premolar and the first lower molar align for efficient tearing, cutting, and slicing of meat/flesh.

Also note that cheek teeth can be brachyodont or hypsodont…
Brachyodont: low-crowned teeth adapted for omnivory
Hypsodont: high-crowned teeth adapted for herbivory

There are also some special cases, for example:

Insectivores sometimes have commissures, which are modified tribosphenic teeth with 3 cusps elongated into sharp crescent-shaped cristas adapted for cracking exoskeletons.

Some seals (piscivores) have sharp, unicuspid cheek teeth for holding slippery prey.

Edentulous is the lack of teeth (anteaters).

Question 5

What is unique about Alces alces and Giraffa camelopardalis dental formulae compared to other large herbivores? Why might these features be retained in these species?

Answer 5

Giraffa Camelopardalis dental formula: I0/3 C0/1 P3/3 M3/3
Alces alces (Moose) dental formula: I0/3 C0/1 P3/3 M3/3

They both lack incisors and canines on the top palette which is utilized for pulling and stripping. This adaptation favours eating leaves off of bushes or trees.

Goats, cows, sheep, deer also have these adaptations.

Question 6

What is unique about Gulo gulo dentition compared to other carnivores? Why might have they developed this adaptation?

Answer 6

Gulo gulo (wolverine) dentition:

• 4 regular incisors and 2 long, larger ones on the top for holding prey
• upper molars rotated inwards to crush bones and frozen tissue
• large canines for stabbing and catching prey

Question 7

What kind of tooth is Phacochoerus aethiopicus tusks? What might they be used for?

Answer 7

Phacochoerus aethiopicus (warthog) tusks are adapted canine teeth.
They are used in sexually-selected duelling and possibly also offers protection from predators.

Question 8

Can you find which teeth make up the carnassial pair in Canis latrans?

Answer 8

Used for tearing and shearing meat

Question 9

What is unique about Castor canadensis front incisors?

Answer 9

Castor canadensis (beaver) front incisors grow continuously. They are thicker and longer for chewing trees. They also have a large overbite to create a gap for fitting trees in mouth and being able to carry wood.

Question 10

How can you describe the diet of Talpa europaea based on its dentition?

Answer 10

Talpa europaea (European mole) dentition and diet inferences:
- large molars for grinding and crushing insect exoskeletons
- characteristic rodent incisors possibly for opening shells/exoskeletons or maybe work like a pair of tweezers since hands are large and less tactile (this, in theory, would help avoid consuming as much dirt)
- canines larger to stab/hold insects

Question 11

Identify types of cheek teeth that Panthera leo, Canis latrans and Ursus arctos have. What is different in Ursus arctos teeth? What does it tell about its diet?

Answer 11

Panthera Leo (lion) and Canis latrans (coyote) are secodonts, meaning they have teeth with sharp, cutting edges, ideal for shearing or slicing through flesh and the specialized carnassial pair (the last upper premolar and first lower molar) designed for shearing meat.

Panthera leo cheek teeth are reduced in size and number, as they are primarily carnivorous and do not require extensive grinding surfaces, while Canis latrans have more generalized molars and premolars compared to lions, as they are omnivorous and need teeth that can handle a variety of foods, including meat, plant matter, and bones.

Ursus arctos are bunodont, meaning they have large, flat molars and premolars with broad grinding surfaces adapted for crushing and grinding plant material, such as roots, berries, and nuts, as well as processing meat.

In conclusion, Panthera Leo is almost entirely carnivorous, Canis latrans are omnivorous but with a preference for meat, and Ursus arctos is omnivorous with a diverse diet.

Question 12

What is the dental formulae for the following species: Ailuropoda melanoleuca, Oryctolagus cuniculus, Myrmecophaga tridactyla, Giraffa camelopardalis, Pongo pygmaeus.

Answer 12

Question 13

Examine the Neovison vison, Ondatra zibethicus, Pekania pennanti, Vulpes lagopus, Vulpes vulpes, and Canis lupus.
What types of hair are found on each?
What is the function of each type of hair?

Answer 13

Neovison vison (mink): fur, vibrissae, and awns
Ondatra zibethicus (muskrat): velli (on tail), fur, awns, vibrissae
Pekania pennant (Fisher): Fur, vibrissae, awns
Vulpes lagopus (Arctic fox): Fur, vibrissae, awns
Vulpes vulpes (Red fox): Fur, vibrissae, awns
Canis lupus (wolf): Fur, vibrissae, awns

vibrissae (whiskers): long, stiff hairs primarily serving as tactile receptors

Guard hairs–
Spines: primarily defensive
Bristles: long, firm with angora growth
Awns: firm, expanded distal region (warmth)

Underhairs–
Wool: Angora growth, soft, insulate
Fur: definitive growth, fine, dense covering
Velli: definitive growth, downy/fuzzy, very fine (peach fuzz)

Question 14

Define heterodont.

Answer 14

In biology, “heterodont” describes animals with teeth of different types and shapes, such as incisors, canines, premolars, and molars, as opposed to homodont animals with teeth of a single type.

Question 15

Eumelanin, pheomelanin, and agouti. What do these mean?

Examine individual hairs from an animal with agouti hair and note the sequence
of colour bands.

Answer 15

Eumelanin and pheomelanin are two types of melanin pigments that determine hair and skin color, with eumelanin producing brown to black colors and pheomelanin producing yellow to red colors. The agouti signaling protein (ASIP) influences which pigment is produced, acting as an antagonist of the melanocortin 1 receptor (MC1R).

Agouti colouration from root to tip:
white-black-grey-black

Question 16

List 2 mammals for each of the following pelage patterns: countershading, disruptive colouration, cryptic colouration, warning colouration, & flagging.

Answer 16

Counter-shading: red fox, mule deer, dolphin
Reverse counter-shading: honey badger
Disruptive colouration: cheetah, zebra
Warning colouration: skunk, wolverine, badger
Cryptic colouration: Arctic fox, Hare
Flagging colouration: white-tail deer, black-tailed prairie dog

Question 17

Are there established populations of albino individuals in the wild? Are there populations of melanistic individuals? Why? Do you know species in which melanistic individuals are common?

Answer 17

Yes, there are established populations of albino and melanistic individuals in the wild, though they are rare. Albino individuals, which lack melanin, often face survival challenges due to poor eyesight and increased visibility to predators, making stable populations uncommon. Melanistic individuals, which have an excess of melanin, are more common in some species, such as leopards (Panthera pardus) and jaguars (Panthera onca), where the dark coloration provides better camouflage in dense forests. Melanism can offer a survival advantage in certain environments, leading to higher frequencies in specific populations. For example, the “black panther” is a well-known melanistic variant of these big cats.

One example of an established albino population in the wild is the albino gray squirrels (Sciurus carolinensis) in Olney, Illinois, USA. This population originated from a single albino squirrel introduced to the area in the early 20th century and has since become a stable and protected community. The albino squirrels are a local landmark and are even celebrated with festivals and legal protections to ensure their survival. While albino individuals typically face survival challenges, this population thrives due to human intervention and lack of natural predators in the area.

Question 18

Why do many desert mammals retain pelage throughout the year?

Answer 18

• shedding and growing a pelt is resource intensive and desserts often lack ample resources
• Do not have drastic temperature changes with the seasons so there is not a need for a “winter coat” or “summer coat”
• Hair is important for UV protection, thermoregulation, and water retention for many mammals in the dessert and likely evolved to keep their coat

Question 19

Where are vibrissae located on mammals? Can you think of more than one
location?

Answer 19

Vibrissae are mostly located all over the face of mammals.

However,
- some species have them on the underside of the leg just under their paws
- dolphins have whiskers around their blow holes

Question 20

What is unique about Dasypus novemcinctus?

Answer 20

Dasypus novemcinctus (nine-banded armadillo) have epidermal scales instead of types of hair like most other mammals.

Question 21

Examine and describe the integument of Castor canadensis tail.

Answer 21

A beaver tail has epidermal scales and a leathery texture. The tail is almost hairless, except for some awns.

Question 22

Compare the horns (both core and sheaths) of Antilocapra americana with
Eudorcas thomsonii. How do they differ?

Answer 22

Antilocapra americana (pronghorn) and Eudorcas thomsonii (Thompson’s Gazelle)

Gazelles do not shed their horns. Pronghorns do not shed their horns either, however, they shed the sheath of their horns annually. The core always remains, that is why they are not considered antlers.

Question 23

Locate the burr, beam, brow tine, bez tine and crown on Odocoileus virginianus,
Odocoileus hermionus, Cervus canadensis, Alces alces (photo) and Rangifer tarandus. How do the general size and arrangement of these racks vary?

Answer 23

Moose and caribou both possess “palms” rather than tines.
White-tail deer, mule deer, and elk have tines. Rule of thumb for determining the brow tine and bed tine is to view the rack from an aerial view. The brow tine is usually smaller and deviates from the beam first, then the bez tine is next to deviate.

Question 24

Looking at several species that have horns and antlers, explain what functions
horns and antlers might be? State the costs versus benefits of having these structures.

Answer 24

Horns and antlers serve several key functions, including defense against predators, intraspecific competition (e.g., fighting for mates or territory), and display to attract mates. For example, antlers in deer are primarily used during the breeding season, while horns in species like bighorn sheep are used year-round for dominance battles.

The benefits of these structures include increased reproductive success and survival, but they come with costs such as high energy expenditure for growth (especially for antlers, which are shed and regrown annually) and increased risk of injury during fights. Additionally, large antlers or horns can make movement through dense vegetation more difficult, potentially increasing vulnerability to predators.

Question 25

Examine the “horns” of Giraffa camelopardalis and compare the structures to that of a true horn and of an antler.

Answer 25

Giraffe ossicones are bony structures covered with skin and hair, differing from true horns and antlers. Unlike true horns (which have a keratin sheath and grow continuously) or antlers (which are shed and regrown annually), ossicones are permanent and fuse to the skull as the giraffe ages. They are used primarily for sparring between males during dominance displays. While true horns serve for defense and competition, and antlers for mating displays, ossicones are unique to giraffes and reflect their specialized evolutionary adaptation. This highlights the diversity of cranial appendages in mammals. - 3rd "horn" sometimes present as a protuberance of the frontals

Question 26

Speculate or research what the evolutionary and ecological significance of antlers in female Rangifer tarandus may be.

Answer 26

Caribou/reindeer live very far north where the snow is incredibly deep in the winter. Females have antlers to help them find and protect food (lichen), especially during pregnancy. After the calves are born, the antlers are dropped (this likely preserves energy that would have been used to carry heavy antlers that can now be used for lactation and calf rearing).

Question 27

Are horns sexually dimorphic?

Answer 27

Yes, in most cases. However, there are some exceptions.

Question 28

Why are antlers shed? Why are horns not?

Answer 28

Short-answer: Antlers grow out of a bony stub, while horns are a keratin sheath over a bone core. Long-answer: Antlers are shed annually because they are primarily used for seasonal mating displays and competition, and shedding allows for the regrowth of larger, more impressive antlers each year. Horns, on the other hand, are permanent structures made of a bony core covered by keratin, serving year-round purposes like defense and dominance, so they are retained throughout the animal's life. This difference reflects the distinct evolutionary roles and energy trade-offs of these structures.

Question 29

Name all the different structures made of keratin that were discussed in lab 2, and the general functions of each.

Answer 29

- Finger and toe nails - Claws - Hooves - Baleen

Question 30

Examine the skeletons of the following: platypus, black rat, rabbit, sloth, domestic cat, tree shrew, Virginia opossum, capuchin monkey, and flying fox. Locate each of the bones described in the axial and appendicular skeleton section. Compare the number of each type of vertebrae in the demonstration skeletons. Identify and explain the adaptations in the skeletal structures in relation to its foraging habits and ecology.

Answer 30

Axial skeleton– skull, spine, and rib cage Appendicular skeleton– fore and hind limbs, pectoral and pelvic girdles

Question 31

Examine the claws of Tupaia glis, Canis lupus, Vulpes vulpes, Neogale vison, Castor canadensis, Gulo gulo, Taxidea taxus, and Phocidae sp. Locate the unguis and subunguis on each. What is the main function of the claws in each of these mammals?

Answer 31

Claw anatomy: Unguis: dorsal plate, curved and encloses the subunguis Subunguis: ventral plate Main Functions of Claws: Tupaia glis (common tree shrew): climbing and digging up insects Canis lupus (wolf): Grip and digging; hold prey Vulpes vulpes (Red fox): capture prey, fight off predators, dig dens, tactile use in food procurement Neogale vison (American mink): help hunt and grip prey; semi-aquatic, catch fish, amphibians, birds, and small mammals Castor canadensis (beaver): grooming, digging, and manipulating objects Gulo gulp (wolverine): climbing trees, move through snow and ice, defence of food or themselves Taxidea taxus (American badger): dig dens, burrows, and to hunt for food Phocidae sp. (earless seal): scratching, grooming, and defence, grip when pulling themselves onto land or ice

Question 32

Examine the hoof of an ungulate. Locate the unguis, subunguis, and frog.

Answer 32

Question 33

How are the forelimbs and hindlimbs of marine mammals structurally different from terrestrial mammals?

Answer 33

There are no hind limbs in marine mammals, as they have tails/flippers instead. However, the forelimbs of terrestrial and marine mammals are homologous structures and show the evolutionary history of these animals. - the digits/filanges make up majority of the flipper however, only 4 digits remain in the flipper - humerus, radius, and ulna are drastically shorter in marine mammals

Question 34

How do the forelimbs, hindlimbs, and tails of jumpers (Lagomorpha) and ricocheting species (Macropodidae) differ from those of plantigrade species?

Answer 34

Lagomorphs and Macropodidae (kangaroos, wallabys, wallawoos, etc.) hind limbs are enlarged and the forelimbs of Macropodidae are reduced in comparison to plantigrade species. Plantigrade species also tend to be bipedal (so forelimbs are more evolved for gripping objects than in Lagomorphs and Macropodidae. Macropodidae have large tails that act as a fifth limb and provide balance.

Question 35

Why are most of the joints (except of hip and shoulder) restricted to move in one plane only in cursorial animals?

Answer 35

This is because limbs are specialized for this type of motion. Linear limbs are stronger in locomotion (think of the frequency of rolled ankles, dislocated shoulders). This means limb movement is restricted to the sagittal plane.

Question 36

Compare the limbs of Cebidae, Sciuridae, Rattus rattus, Felis catus, Canis [lupus] familiaris, Dasypus novemcinctus, and Lagomorpha. What kind of locomotion do they each exhibit?

Answer 36

Cebidae (monkeys)– Arboreal - opposable digits - sharp claws Sciuridae (squirrels)– Scansorial - Sharp, strong claws Rattus rattus (Black rat)– Cursorial Digitigrade - limbs capable of moving in several planes - reduced number of toes - metacarpals and metatarsals do not touch surface - elongation of the metacarpals and metatarsals Felis catus (Domestic cat)– Cursorial Digitigrade - limbs capable of moving in several planes - reduced number of toes - metacarpals and metatarsals do not touch surface - elongation of the metacarpals and metatarsals Dasypus novemcinctus (Nine-banded Armadillo)– Cursorial Digitigrade - limbs capable of moving in several planes - reduced number of toes - metacarpals and metatarsals do not touch surface - elongation of the metacarpals and metatarsals Lagomorpha (Rabbits, Hares, and pikas)– Saltatorial (jumping/sprining) - Progressing by series of leaps - Hind limbs provide main propulsive force

Question 37

Give examples of a mammal species that have cursorial (digitigrade and unguligrade), saltatorial, and graviportal locomotion. Describe the limb modifications of each species and the habitat that these species occur in. What advantage does saltatorial motion have over cursorial motion?

Answer 37

What advantage does saltatorial motion have over cursorial motion? Saltatorial motion (hopping) offers several advantages over cursorial motion (running). It is highly energy-efficient, especially in arid environments, as elastic energy stored in tendons reduces metabolic cost. Hopping allows for rapid bursts of speed and agility, aiding in predator escape, and enables animals to navigate uneven terrain or obstacles more easily. Additionally, the upright posture minimizes heat absorption in hot climates, and the unpredictable movement can confuse predators. Saltatorial motion also provides better access to elevated food sources, such as leaves or fruits in trees. These adaptations make it highly effective for species like kangaroos in their ecological niches.

Question 38

Compare the limb structure and general body shape of Talpa europaea and Heterocephalus glaber with that of Tupaia glis. What modifications for fossorial life are present in the first two?

Answer 38

The mole and the mole-rat have shorter fore-limbs closer to their bodies than the shrew. Their overall figure is denser and likely more muscular. The mole has enlarged hands for digging. Fossorial life– - reduction of external body projections - reduction in vision - increase of tactile receptors - enlargement of forefeet and claws - strong musculature of the limbs and pectoral girdle - could use large incisors for digging

Question 39

Bones serve as the surface for muscle attachment. Compare the femur and humerus of the fossorial and arboreal species. What differences do you see and why might they differ in shape and structure?

Answer 39

The femur in fossorial is much shorter and thicker and the humerus and ulna are thicker and closer together. This is characteristic of strengthening for a specialized movement. Arboreals have these thinner, more elongated humerus and femurs adapted for a larger range of motion (rather than one specific/specialized movement).

Question 40

Ornithorhynchus anatinus digs nest burrows into banks of streams where it feeds underwater. Examine the forefeet and explain how they are adapted for this.

Answer 40

The platypus has... - elongated, sharp claws - similar forelimbs structure as moles, adapted for strength (humerus, ulna, and femur are shorter and thicker) - shoulder-over-foot positioning ideal for scooping back soil/earth

Question 41

Think about the tail structure of a cetacean with that of a fish. The fish undulates laterally. What advantage is there in undulating dorsoventrally like whales do?

Answer 41

Whales are able to use their tails in different ways than fish. Likely beneficial for surfacing water to breathe quicker. Evolved from a terrestrial undulate, they retained this lateral motion that is based on their physiology and is important so the spine is not damaged.

Question 42

Prehensile tails have evolved in diverse mammalian groups. List mammals having a prehensile tail and the continents on which each is found.

Answer 42

Question 43

Name a mammal that has each of the following preferred gaits: walk, bound (aka saltatorial), amble, trot, pace and gallop.

Answer 43

Walk: tigers Bound (saltatorial): rabbit Amble: elephants, lemurs Trot: Pronghorn Pace: Camels Gallop: horses, cheetahs

Question 44

Examine the forelimbs of Glaucomys sabrinus and Vespertilionidae/Pteropodidae. How does their patagium differ? What type of locomotion do they each use?

Answer 44

Patagium: membrane or fold of skin between the forelimbs and hindlimb on each side of a bat or gliding animal. Vespertilionidae and Pteropodidae (evening bats and megabats) have true wings because the skin is stretched along the elongated finger bones. Glaucomys sabrinus (flying squirrels) have regular rodent hands and feet with extra skin at their sides that acts as a glider.

Question 45

How do the claws of Talpa europaea and Ictidomys tridecemlineatus compare? What kind of adaptations do they show?

Answer 45

Talpa europaea (European mole) and Ictidomys tridecemlineatus (Thirteen-lined ground squirrel) both have elongated claws useful for digging. However, the ground squirrel has sharper claws while the mole has duller but wide claws. This is likely because the ground squirrels have a diverse diet that requires the ability to hold and maneuver their food. Ground squirrels also forage above ground and need to protect themselves from predators while moles stay below ground for most of their life.

Question 46

Locomotion: when looking at the skeletons/photos of the platypus, Virginia opossum, flying lemur,and North American mole, what can you tell about its limb adaptations and how it moves?

Answer 46

The platypus has webbed feet and flattened limbs for efficient swimming, while the Virginia opossum possesses grasping hands and feet with a prehensile tail for climbing and terrestrial movement. The flying lemur (colugo) has elongated limbs and a patagium (skin membrane) for gliding between trees, and the North American mole features short, powerful forelimbs with large claws for digging through soil. Each species' limb adaptations reflect their unique locomotion strategies—swimming, climbing, gliding, and burrowing—tailored to their specific ecological niches.

Question 47

Define the following terms: homodont, diprotodont, and polyprotodont.

Answer 47

Homodont: means having teeth that are similar in shape and size Diprotodont: most diprotodonts have three pairs of incisors in their upper jaws, but this number Is reduced to one pair in wombats. Diprotodonts lack lower canines and upper canines vary in shape from low and smooth to having many sharp, curved ridges. Polyprotodonts: any marsupial of the group Polyprotodontia are characterized by four or more upper incisor teeth on each side of the jaw (includes the opossums and bandicoots)

Question 48

Examine the dentition of the Ornithorhynchus anatinus, Didelphys virginianus, Thylacinus cynocephalus, Isodon macrourus, Macropus rufus, and Myotis spp. Can you tell if they are homodont, diprotodont or polyprotodont? Which species does not have one of the listed dentition types? How would you describe its teeth?

Answer 48

Virginia opossum– polyprodont Thylacine– heterodont; polyprodont Northern brown bandicoot– polyprodont Red kangaroo– Diprotodont Mouse-eared bats (microbes)– polypotodont The platypus does not have any teeth; instead they have a duck-like bill and crushing gums in the back of the mouth/jaw. Platypus– Endentulous

Question 49

True or false? Dental formulae are based on heterdont teeth.

Answer 49

True. The formula ICPM assumes there are variations in teeth type (incisors, canines, premolars, and molars).

Question 50

Based on their teeth, what can you infer about an animal’s diet?

Answer 50

Enlarged incisors are characteristic of carnivores as they are for tearing flesh and holding/stabbing prey. Also the presence of the carnassial pair is a key give away. Flattened molars are for herbivores as they are adapted for grinding down course vegetation. A mix of the two would indicate omnivory. Insectivores have specialized teeth for crushing insect skeletons, or sometimes lack teeth entirely.

Question 51

What might the function of the comb-shaped colugo incisors be?

Answer 51

Flying lemurs use their comb shaped teeth to chew leaves and young shoots from trees. They also help with straining food and grooming.

Question 52

List 3 features for each of the groups Prototherians, Metatherians, and Eutherians that are not found in the other two groups.

Answer 52

These three groups are mammalian clades or subclasses. Prototherians include echidnas and platypus. Metatheria includes marsupials and their closest extinct relatives. Eutheria includes "true mammals" or placenta mammals. Prototherians lay eggs, metatherians give birth to underdeveloped young that continue to develop in the pouch, and eutherians give birth to fully developed young.

Question 53

Why are Monotremes considered primitive mammals?

Answer 53

Monotremes are considered primitive animals because they lay eggs, a trait shared with reptiles and birds, unlike most other mammals who give live birth; they also possess skeletal features reminiscent of ancient reptiles, like a single cloaca and complex shoulder girdle with additional bones not found in other mammals, indicating their evolutionary lineage is close to the origins of mammals.

Question 54

Epipubic bones exist in most Marsupials, but not all of them. Can you think of any function they may serve?

Answer 54

Epipubic bones are paired bones articulating with the pubis and projecting cranially in the ventral body wall, present on the pelvic girdle of cynodonts, monotremes, and marsupials. These bones were commonly thought to be related to pouch support in marsupials and more recently associated with locomotion.

Question 55

Integument and Locomotion: Determine the types of hair found on the echidnas, the star-nosed mole, the hedgehog, the masked shrew, the hoary bat, and the Arctic shrew. Which growth does each hair type exhibit? What can this tell you about the characteristics of the habitat in which those animals are living?

Answer 55

Question 56

Compare the morphology of the colugo, flying squirrel, and bat patagia (wings).

Answer 56

The colugo (flying lemur) and the flying squirrel are not true flying mammals. Instead they a gliding species. Bats, however, are true flying-mammals. This is because their wings are skin stretched along the lengthened forelimb digits. Gliding mammals do not have these structures, but extra skin that acts as a parachute, while still preserving the classic mammalian structure of the forelimbs.

Question 57

List three examples (adaptations or traits) of convergent evolution between marsupials and placental mammals?

Answer 57

Prehensile tails are observed in both marsupials and eutherian mammals. For example, the opossum and many species of monkey. Caenolestidae are diprotodont marsupials that resemble a shrew in many ways. This is a common case of marsupial/eutherian convergent evolution: is the great similarities between small, shrew-like marsupials and many eutherian rodents (physical form, omnivorous dentition, etc.) Carnivorous eutherian and marsupial mammals share many traits as well, such as enlarged canines for stabbing and catching prey. We also see the convergent evolution of saltatorial locomotion in lagomorphs and macropodidae, which is a classic case of the locomotion evolved for most efficient movement on the rough, vast terrain.

Question 58

Condylura cristata is very well adapted to a particular lifestyle. Which one is this? How can you tell? What is the function of the “star nose”?

Answer 58

The star-nosed mole is very well adapted to a fossorial lifestyle. It has the classic physiological adaptations for burrowing, such as shortened/thickened ulna and radius and femur. Their nose is well-adapted for finding their way around in the dark and for hunting their insect prey. They also have these protruding incurs with enlarged canines. This pair is perfect for capturing both small and larger prey.

Question 59

The defunct order Insectivora was decided based mostly on morphology. However, it was broken up due to DNA analysis. There is still debate about speciation and classification based on morphology versus DNA analysis. What do you think? Are both methods valid?

Answer 59

Insectivora is the former "wastebasket" order that was restructured and reorganized into Euliptophyla, with four families (Soricidae, Solenodontidae, Talpidae, and Erinaceidae). It contains the smallest mammals to rabbit-sized mammals. It is characterized by reduced/absent jugals/zygomatic arches, as well as vibrissae and one other type of hair. I believe there is validity in both methods, however, DNA analysis shows evolutionary decent. When we compare both of these methods, we can identify what traits are result of convergent evolution and which are derived features.

Question 60

Examine the forelimb and manus structure of a Chiropteran. How does it compare to a limb of a non-flying species?

Answer 60

The forelimb bones are thinner and longer than the forelimb of most other mammals. They provide a frame for the stretched skin of the patagium. Chiropterans have five digits but the "thumb" is reduced to a small, short spur at the top of the patagium.

Question 61

Compare the form of Pteropus sp. to other Chiropterans. Why does this species look so different?

Answer 61

Megabats look different from other Chiropterans because they're adapted for frugivory, rather than insectivore. Flying foxes have simple ears because they use their keen sense of smell and large, binocular eyes to seek out fruit to eat. This varies from other bats that rely on sound and echolocation to navigate their nocturnal habitat. They are also much larger, as their food source allows for larger growth.

Question 62

Review the “Bats of Saskatchewan”. Which species are at-risk and what are some of the risks they face? What are some adaptations our bats in Canada have compared to other regions?

Answer 62

There are 8 species of bats found in Saskatchewan (some migrate and some overwinter). They are all members of the family Vespertilionidae or the smooth-faced bats. They are all insectivorous, eating a variety of insects with species-based preferences. Of the 8 species, the following are endangered: Eastern red bat, Hoary bat , Northern long-eared bat , silver-haired bat, and the Little Brown Bat. Only the Big Brown Bat and the Western small-footed bat are not at risk. Their biggest threats are likely habitat loss and depletion of food source with the use of insecticides. There is also the many diseases, such as white-nose syndrome. As mentioned before, some of the bats have exceptional hibernation adaptations to survive the harsh winter, or some migrate away. They are also social creatures and roost together, which can help with retaining warmth.

Question 63

What links the armadillos and the anteaters into the super-order Xenarthra?

Answer 63

Shared traits between armadillos and anteaters include: extra vertebral joints (The lumbar vertebrae of xenarthrans have extra joints that strengthen their lower backs and hips. This helps them use their forelegs for digging, which is how they get food), low metabolic rates, reduced dentition, and low body temperatures (related to slow metabolism).

Question 64

The pangolins share a similar morphology to the armadillos, yet they are not closely related. What are some differences between the two families and what purpose do they serve?

Answer 64

The quickest way to tell these apart is that armadillos have pointed ears while pangolins have small, rounded ears or ear holes. Pangolins have keratin scales, a long, toothless snout, and a strong stomach for crushing insects. Pangolins also have a prehensile tail (armadillos do not). Armadillos have bony plates (osteoderms) covered in keratin and a thin layer of skin and short snouts with teeth specialized for cracking insects. Pangolins are native to Africa and Asia; Armadillos are native to the Americas. Lastly, only the nine-banded armadillo can roll into a ball, while all pangolins can.

Question 65

Despite being a common characteristic amongst primates, not all species have an opposable pollex. Why might this be?

Answer 65

Opposable pollex: (opposable thumb) a thumb that can touch the tips of the other fingers on the same hand. The pollex is the anatomical term for the thumb. Tarsiers, marmosets, and some New World monkeys do not have opposable thumbs. Opposable thumbs are sometimes lost to evolution because the species does not need them or not having opposable thumbs is more advantageous for locomotion. For example, spider monkeys have small thumbs for swinging from branches and colobus monkeys have reduced thumbs because they do not need them.

Question 66

Members of family Hominidae lack a tail. How does this benefit or disadvantage their lifestyle?

Answer 66

Benefits: lack another appendage that can be injured or grabbed in fighting/escaping predator, wouldn’t get in the way in bipedal locomotion Disadvantages: tails can be used for balance and making faster turns when running (cheetah), prehensile tails are useful for tree-dwelling species

Question 67

List three defining characteristics of a carnivoran skull. How can you distinguish between Feliformia and Caniformia? What might account for this difference(s)?

Answer 67

Canidae is characterized by large conical canine teeth, the presence of a sagittal crest, and well-developed zygomatic arches. Feliformia has a short, blunt snout; five-toed forefoot with separated pollex, well-developed carnassials ( the large upper premolar and lower molar teeth of a carnivore, adapted for shearing flesh), and cylindrical, fury tails. Caniformia also have five-toed forefoots but a four-toed hindfoot with vestigial pollex, bushy tails and elongated snouts, as well as long legs and up-right years.

Question 68

Male Odobenus rosmarus use their tusks for fighting, dominance, and display meaning tusks are directly involved in sexual selection. However, females also have prominent tusks. What could they be used for?

Answer 68

Walruses also use their dusks for digging and drudging up clams. Female walruses may use their tusks to protect their young as well. Walruses also use their tusks as ice-picks to poke holes in the ice so they can emerge to breath and pull themselves onto the ice or rocky shores.

Question 69

Despite their normally vegetarian diets, the Ailuropoda melanoleuca and Ailurus fulgens are included in Order Carnivora. Do you think they belong here? Why or why not?

Answer 69

The Giant Panda (Ailuropoda melanoleuca) is included in Ursus with the other bears, despite being herbivorous. I think this is appropriate because pandas have retained characteristics of bears, and therefore carnivores, such as their large canines and powerful jaws. Because the Giant Panda still so much resembles other bears (omnivorous or carnivorous), it would be inappropriate to deviate them from their lineage. The Red Panda (Ailurus fulgens) is placed in between Ursus (bears) and Mustelids (weasels, badgers, otters, polecats, martens, grisons, and wolverines). I feel that this placement is also appropriate and, therefore, including the Red Panda in Carnivora despite being herbivorous is also appropriate. Again, the Red Panda retains the traits of its carnivorous lineage and is also phenotypically similar to both Ursidae and Mustelidae.

Question 70

Examine the Tupaia glis skeleton. Can you find any differences between it and the Talpa europaea skeleton?

Answer 70

The Tree shrew skeleton obviously lacks the traits that the European mole possesses that are adapted for a life below ground, such as large claws, thick, shortened limbs bones for digging, backward facing hind-limbs, etc.. Instead it has traits characteristic of their arboreal lifestyle (slim and long limb bones, short claws for climbing, long tail that is sometimes prehensile).

Question 71

Both families of sloth (Brachypodidae and Megalonychidae) and the gibbons (family Hylobatidae) are very well adapted to an arboreal lifestyle. What characteristics do they share? Are they used in the same way?

Answer 71

Both sloths and gibbons share long limbs and strong grips, adaptations essential for arboreal life. Gibbons use their long arms for brachiation (swinging through trees) and have hook-like hands for grasping branches, while sloths use their long limbs and curved claws to hang and move slowly through the canopy. Additionally, both have flexible joints for navigating complex tree structures, though gibbons rely on speed and agility, whereas sloths prioritize energy efficiency and camouflage. These differences reflect their distinct lifestyles: gibbons are active, fast-moving primates, while sloths are slow, sedentary mammals.

Question 72

Examine the claws on the Mustelidae family. Whose are the largest and smallest? Why might this be?

Answer 72

The wolverine (Gulo gulo) has the largest claws, which are robust and curved, adapted for digging, climbing, and tearing through frozen carcasses in their harsh northern habitats. In contrast, the least weasel (Mustela nivalis) has the smallest claws, as its slender body and small size are suited for hunting small prey like mice and voles in narrow burrows, where large claws would be unnecessary.

Question 73

Compare the skulls of Gulo gulo, Martes americanus , and Pekania penneti. What differences do you see?

Answer 73

Gulo gulo (Wolverine): The skull is large and robust, with strong, broad zygomatic arches and a powerful jaw. The teeth, particularly the carnassials, are well-developed for crushing bones and processing tough prey. The skull shape reflects its role as a scavenger and predator capable of taking down large prey or breaking into frozen carcasses. Martes americanus (American Marten): The skull is smaller and more slender compared to the wolverine, with a narrower rostrum (snout). The teeth are sharp and suited for a diet of small mammals, birds, and insects. The skull reflects its agile, arboreal lifestyle and preference for smaller prey. Pekania pennanti (Fisher): The skull is intermediate in size between the wolverine and marten, with a strong, elongated rostrum. The teeth are robust, adapted for hunting porcupines and other medium-sized prey. The skull structure reflects its versatility as a predator, capable of climbing and tackling prey larger than itself. In summary, the wolverine's skull is the most robust for crushing and scavenging, the marten's skull is slender and adapted for small prey, and the fisher's skull is intermediate, reflecting its ability to hunt larger, more challenging prey. These differences highlight their adaptations to specific ecological niches.

Question 74

What differences and similarities in body structure and lifestyle can you see between aardvark and anteater?

Answer 74

Aardvarks and anteaters are both insectivores with elongated snouts that help them suck ants and termites out of mounds. However, they have many anatomical differences. The Aardvark lives in sub-Saharan Africa, while the Anteater is from Central and South America. Aardvarks are nocturnal and anteaters are diurnal. Anteaters have long, tapered snouts that are wide near the face; aardvarks have tube-shaped snouts like a pig. Aardvark claws are blunter and anteater claws are longer and knife-like. Respectively, their ears are long like a rabbit vs short. Anteaters have long, dense hair and a bushy tail; aardvarks have thin course hair. These two mammals are a prime example of convergent evolution.

Question 75

Do some research on the historical development of Afrosoricida taxonomic position and name the reasons why this order is separate from Eulipotyphla (former Insectivora).

Answer 75

The order Afroscoricida includes tenrecs and golden moles, which were once classified within the former order Insectivora alongside shrews, moles, and hedgehogs. However, molecular and morphological research let to the separation of Afrosoricida from other insectivorous mammals and in its placement within superorder Afrotheria. Traditionally, insectivorous mammals with small body sizes, simple teeth, and burrowing or fossorial behaviours were grouped under the order Insectivora (a now obsolete taxonomic group). Advances in molecular genetics revealed that tenrecs and golden moles are more closely related to elephants, hyraxes, and aardvarks than to true insectivore's DNA sequencing. Particularly, studies using mitochondrial and nuclear genes, placed tenrecs and golden moles within Afrotheria, a clade of mammals that originated in Africa. This led to the recognition of Afrosoricida as a separate order within Afrotheria. While Afrosorica and Eulipotyphla share some superficial traits due to convergent evolution, they differ in: ear bones, placental structures, and skull and dental features. Lastly, we have biogeographical evidence: Africa and Madagascar vs Eurasia, North America, and Africa

Question 76

What is the main distinguishing feature of a Lagomorph skull compared to a Rodent skull?

Answer 76

Lagomorph skulls have hypsodont cheek teeth and two incisors. All teeth are rootless and grow continuously. Lagomorphs also have smaller peg teeth positioned behind the incisors. Lagomorphs have a more flexible jaw that allows both side-to-side and up/down movement for grinding plant material. Rodent skulls have a single pair of arc-shaped, chisel-edged, ever-growing incisors and pronounced diastema. Rodents have a more specialized gnawing motion, primarily using an up/down movement.

Question 77

Pika species differ in their social behaviour. Mountain-dwelling species are mostly solitary, marking and defending their territories from each other, while burrowers live in family groups, defending their mutual territories. How can you explain these differences from behavioural ecology point of view?

Answer 77

In rocky alpine habitats, food resources (vegetation) are scattered, and pikas must individually defend their territories and store haypiles for winter. In grasslands, food is more abundant and evenly distributed, allowing for cooperative foraging and burrowing. Group living enhances protection against predators, which isn't as applicable for mountain pikas since they rely on rock crevices for protection.

Question 78

Identify the skull condition (zygomasseteric system) for each rodent. Why might they have or need different muscle strengths in the jaw?

Answer 78

Protrogomorphous– Mountain Beaver Primitive, weak masseter Least specialized Sciuromorphous– Squirrels, beavers Zygomatic plate Strong gnawing Hystricomorphous– Porcupines, capybaras Enlarged infraorbital foramen Powerful chewing Myomorphous– Mice, rats Hybrid of sciuro and hystrico Versatile gnawing and chewing

Question 79

List four ways in which the tail of rodents is adapted to different habitats.

Answer 79

Elephant shrews have a scaly tail adapted for rougher surfaces. Lagomorphs have a short or sometimes absent tail adapted to not get in the way or caught in vegetation when running. Beavers have a large, flat, scaly tail used for swimming and building dams. Pocket gopher tails are adapted to provide sensory information.

Question 80

Some rodents are hibernators and some are not. Describe strategies that enable species to maintain body temperature and activity throughout the winter.

Answer 80

- Social rodents hibernate in burrows together to maintain temperature (social thermoregulation) - Mountain pikas cache food (haypiles) and stay active year-round (hoarding behaviour) - Non-shivering thermogenesis; some rodents (like voles and mice) have brown adipose tissue (BAT), which generates heat without shivering. - Grow thicker coats in winter - Rodents that remain active increase food intake to fuel metabolism - Build a variety of kinds of insulated shelters or nests - Subnivean (below snow) lifestyle; voles and lemmings create tunnels beneath the snow, escaping the elements and grazing on vegetation below - Dietary flexibility and opportunistic foraging

Question 81

Identify the enamel and dentine of incisors of a rodent. Why are they structured that way?

Answer 81

Rodent incisors have dentine inside and are covered in enamel. This serves as a self-sharpening mechanism and allows for continuous growth, as well as makes for efficient gnawing and digging.

Question 82

Most rodents are nocturnal or crepuscular. List 3 rodents that are diurnal. Why do you think they are diurnal?

Answer 82

Eastern Gray Squirrel– relies on daylight for better vision while navigating branches, avoids nocturnal predators, efficient foraging BTPD– visibility in grasslands essential to detect predators and rely on sunlight for warmth Cape ground squirrel– forages in the morning and late afternoon to avoid extreme midday heat

Question 83

For all skulls present write down dental formulae and identify types of teeth (shape and height of incisors, presence of teeth of different types). African forest elephant, Cape Hyrax, horse, moose, collared peccary, dugong, white-tail deer, mule deer, caribou, giraffe, Cuvier's beaked whale, beluga whale, Thomson's gazelle, goat.

Answer 83

Key Terms Explained: Tribosphenic/Quadritubercular: Primitive molar patterns (not common in most listed species; seen in early mammals). Brachyodont: Low-crowned teeth (suited for soft diets). Hypsodont: High-crowned teeth (resistant to wear, for abrasive diets). Selenodont: Crescent-shaped ridges (common in ruminants like deer, goats). Lophodont: Transverse ridges (elephants, horses, dugongs). Bunodont: Rounded cusps (omnivores like peccaries, hyraxes). Secodont: Sharp, cutting teeth (carnivores; not present here). Homodont: All teeth similar (whales).

Question 84

How do you distinguish between a white-tail deer skull and a mule deer skull (both male)?

Answer 84

Mule deer antlers are often bifurcated (forked), while whitetail antlers typically have single tines branching from the main beam.

Question 85

Think of environmental pressures that might have forced the early ancestors of Cetaceans to become secondary aquatic.

Answer 85

Predation, lack of food, extremely hot or dry environments

Question 86

How do Mysticeti and Odontoceti differ in their adaptations for hunting prey?

Answer 86

Mysticeti (or baleen whales): - Different taxa vary in how they use them to capture prey, with complex relationships between baleen form, plate type, feeding behaviour, and food preferences. - Do not echolocate - often feeding on various relatively-small prey - Grey whale is a bottom feeder Odontoceti (or toothed whales) - Specialize on scarce food resources, each species adapt for different sorts of food - Sight is poor-developed, olfaction is almost absent - Hearing is very well-developed –echolocation by sonar - Polygynous, very sociable, most live in the groups - some hunt in groups while others access deep ocean hunting grounds with less competition - the Pigmy Sperm Whale feeds on squid using suction-feeding by rapidly depressing their tongue

Question 87

Looking at the skull of the beluga, how can you tell that it is adapted to an aquatic life and that it is a good diver?

Answer 87

(1) Fusiform shape (spindle-like shape; think an oat seed) (2) blowhole on the top of the skull (aquatic) (3) large cavity where the melon goes because the best divers have the biggest melons in order to sense their surroundings in the deep ocean environment

Question 88

Compare and contrast paraxonic and mesoxonic foot structures in ungulates. Could you think of any advantages and disadvantages of each of foot types?

Answer 88

Ungulates have specialized unguligrade limb structure, where the distal limb elements are elongated but reduced in weight. The metapodials are fused, some digits reduced or lost, and weight is bore on the filanges. This allows for rapid cursorial motion. Perissodactyls have mesoxonix foot structures meaning the weight-bearing axis passes directly through the third digit. Artiodactyls have paraxonic foot structure meaning the weight-bearing axis passes between the third and fourth digits. Furthermore, Perissodactyls have rotating ankle joints while Artiodactyls do not. Perissodactyls are more adapted to flat landscapes and speed where they can dig into the ground with their enlarged middle digit and make quick turns or changes of direction. Artiodactyls are more adapted for varied terrain and graceful/precise movement, with two toes that provide balance and ankles that cannot be rolled.

Question 89

Perissodactyls are very large animals (e.g. rhino) and one hypothesis to explain this has to do with their digestive system. Any idea what this could be? Why do you think other herbivorous species evolved ruminant digestive systems?

Answer 89

Artiodactyls have a multi-chambered stomach that houses micro-organisms that break down cellulose and plant toxins. They periodically regurgitate and chew the cud so they secrete saliva (which contains a natural antacid which helps to buffer the rumen or first compartment of the stomach). This digestive system is slow by efficient, allowing for small quantities of high quality food. Perissodactyls have a simple stomach with long intestines and a handgun fermentor. This digestive system is rapid but less efficient because they are able to take in large quantities of lower quality food. Artiodactyls are likely adapted for environments where food sources are more scarce but high-quality. For example, caribou feeding on lichen patches. Perissodactyls are more adapted for environments where food is abundant but in low quality, like semi-arid grasslands. Artiodactyls may also observe higher predatory pressure, so they have to keep moving and, therefore, can afford less time grazing. Ruminant digestive systems may have evolved in response to artiodactyls needing to survive on less food, whether that is because of lower availability of food or less time sedentary that can be spent grazing.

Question 90

Compare different types of combat weaponry among artiodactyls. Could you think of why some species rely on cranial weaponry (horns and antlers) and others on complex dentition (enlarged incisors and canines)?

Answer 90

The evolution of combat weaponry in artiodactyls (even-toed ungulates) is shaped by factors like sexual selection, ecological pressures, and biomechanical constraints. The choice between cranial weaponry (horns, antlers, ossicones) and dentition-based weaponry (enlarged canines, incisors, tusks) depends on several key factors: 1. Cranial Weaponry (Horns & Antlers) Examples: Deer (antlers), bovids (cattle, goats, antelope – true horns), giraffids (ossicones). Advantages: Long reach: Effective in head-to-head clashes, keeping opponents at a distance. Visual signaling: Large antlers/horns advertise fitness to rivals and mates. Non-lethal combat: Often used in ritualized fights rather than fatal encounters. Why Some Species Use Them: Sexual selection: Males with larger/more elaborate horns/antlers have higher mating success (e.g., red deer stags). Open habitats: Species in grasslands or savannas (e.g., bison, antelope) benefit from long-range weaponry. Energy allocation: Antlers are shed and regrown annually, allowing for intense seasonal competition. 2. Dentition-Based Weaponry (Tusks, Canines, Incisors) Examples: Pigs (tusks from canines), musk deer (sabre-like canines), hippos (enlarged incisors & canines), water deer (elongated canines). Advantages: Close-quarters combat: Effective in dense forests or aquatic environments where grappling is key. Multipurpose use: Tusks can be used for digging, stripping bark, or defense against predators. Less energetically costly than growing large antlers annually. Why Some Species Use Them: Habitat constraints: Forest-dwelling species (e.g., muntjac, musk deer) rely on slashing weapons in tight spaces. Alternative mating strategies: In some species (e.g., babirusa), tusks may be more for display than direct combat. Predator defense: Hippos use their massive canines against lions or rival hippos. Why the Difference? Ecological Niche: Open-habitat species benefit from long-range weaponry, while forest-dwelling species rely on close-combat tools. Mating Systems: Intense male-male competition (e.g., elk, bighorn sheep) favors large, conspicuous weapons like antlers/horns. Predation Pressure: Some dentition-based weapons (e.g., hippo tusks) serve dual roles in combat and predator defense. Biomechanics: Heavy cranial weapons require strong neck muscles, whereas tusks rely on jaw strength. Conclusion: Horns/antlers dominate in open habitats with intense male competition. Tusks/enlarged teeth are more common in forest-dwelling or omnivorous species where close combat or tool-like functions are advantageous.

Question 91

Horns of bovids vary greatly in size and shape among species. How could you explain this?

Answer 91

The variation in bovid horns is driven by sexual selection (larger, more elaborate horns improve mating success), ecological adaptation (e.g., curved horns for locking in combat vs. straight horns for stabbing), and species recognition (distinct shapes help avoid hybridization). Habitat also plays a role—open plains favor long horns for clashing, while dense forests may select for shorter, sharper horns for close-quarters defense.