Lecture Final Flashcards
How are foraging modes defined? What are the two major foraging modes we talked about in class?
Foraging modes traditionally defined based on behavioral patters of locating and capturing prey. Two foraging modes talked about were 1.) Sit-and-wait foraging (ambush foraging) and 2.) Active foraging (wide foraging).
Compare and contrast Sit-and-Wait foraging with Active foraging.
Sit-and-Wait Foraging Use little time and energy searching for prey items Stationary behavior and attack mobile prey when detected within field of vision Most energy spent on capturing and handling prey items **often more territorial and generally wait for food to come into territory. **generally seen in Iguanians Movement times, rates, & percentages are lower in sit-and-wait foragers Lower/limited endurance & higher sprint speeds in sit- and-wait foragers Daily energy use & intake lower in sit-and-wait foragers Active Foraging Actively move through environment searching for prey items Much energy used during searching phase Little energy used in capture of prey item **generally smaller prey so they don’t have to wrestle with it to catch and eat it. **generally seen in non-iguanian squamates Activity body temperatures higher in active foragers BOTH are foraging modes exhibited in reptiles and amphibians.
What is the Optimal Foraging Theory?
Traditional explanation for the evolution of foraging modes In presence of competition, individuals best able to exploit resources should have selective advantage Fine-tuned by natural selectionultimate pay-off should be greater reproductive success Overly simplistic theoryforaging is complex Few studies support associated predictions
What are some factors that influence foraging behavior?
External factors include prey availability, predation risk, social interactions (e.g.. competition), habitat structure, and opportunities for thermoregulation. Internal factors include hunger, learned experiences, age, sex and reproductive state, etc. Historical factors include sensory limitations, morphological characteristics (e.g. mouth shape, head size), physiological constraints (sprint speed), and behavioral set (conservative foraging mode)
What are the different ways that amphibians and reptiles can detect prey? Specifically, how do Caecilians, Batrachians, Crocodylians, Chelonians, and Squamates detect?
Prey may be detected by visual, chemical, tactile, and/or thermal signals May have reliance on a single system or used in combination Caecilians: Tentacles for chemosensory cues Batrachians: Visual cues Crocodylians: Visual and tactile cues Chelonians: Visual, tactile, & chemical cues Squamates: Use all forms Subgroups may primarily use one sense
Define and describe Visual Prey Detection.
Primarily important for the sit-and-wait predators Common in iguanians and cordylids; also most anurans Success in prey capture generally requires binocular perception of prey item Align head (and body) with prey Exceptions: Chameleons Large and well-developed eyes Prey movement often required
Define and describe Chemosensory Prey Detection.
Three avenues for detecting chemical cues from the environment 1. Olfaction: Nasal chamber 2. Vomerofaction: Vomeronasal (Jacobsonʼs) organ 3. Taste (gustation): Oral cavity Olfaction and vomerofaction rely on airborne and/or surface chemical cues Olfaction: Long-distance detection; Presence of food and general location Vomerofaction: Short-distance detection Gustation: Primary function is food discrimination Involves taste buds of oral cavity
In what groups is chemosensory prey detection found in amphibians and reptiles? What is the traditional and new view of how this was derived in squamates?
Olfaction and vomerofaction: Important in “scleroglossan” squamates and plethodontids salamanders Fine-tuned vomerofaction in snakes and other deeply fork- tongued squamates Recent evidence in crocodylians and aquatic turtles; Historically thought to be primarily visual and tactile focused The “Squamate Story” Traditional theory relating squamate diversification; Evolution of vomerofaction-based foraging system in “scleroglossans” from ancestral visual-based system as seen in iguanians Now: Iguanian condition is derived and vomerofaction is ancestral Did evolution of sit-and-wait foraging aid in iguanian diversification? Evolution of vomerofaction may still have allowed for the diversification of squamates
Define and Describe Auditory Prey Detection.
All amphibians and reptiles can hear and/or sense vibrations Generally, not thought to be important for foraging; Recent anecdotal evidence suggestions prey may be detected by auditory or vibration related cues in some groups
Define and describe Thermal Prey Detection.
Infrared (long wavelength light) receptors evolved multiple times in boids and pythonids, and once in Crotalinae Multiple labial pits in boid and pythonids Single pit (=loreal pit) between eye & nostril in pit vipers Organ consists of thin, highly enervated membrane stretched across open cavity Structure allows precise detection of distance & direction In rattlesnakes, head cooled when snake is excited Allows even more precise thermal differentiation (0.003o C) Pit organs are enervated by trigeminal nerve” Wired to visual cortex Thermal images are integrated with visual images Snakes see the thermal profile of infrared source superimposed on visual image
Define and Describe Tactile Prey Detection.
Known method of detection, but still poorly understood Mechanoreceptors in skin Lateral line system in aquatic amphibians Crocodylians? Enervated epidermal appendages Barbels around lower jaws in many aquatic turtles Lure-like tongue of Alligator Snapping Turtle (Macrochelys temminckii) Head tentacles in the Tentacled Snake (Erpeton tentaculatum)
Where in amphibians and reptiles did the projectile tongue feeding evolve?
Projectile tongue independently evolved in different groups of amphibians and reptiles Amphibians: anurans and some salamanders Reptiles; within Chamaeleonidae
Describe projectile tongue feeding in Caudata.
Most terrestrial salamanders feed by capturing prey with a large, moist/sticky tongue Tongue barely protrudes from the mouth (only a few millimeters) (Non-chamaeleonid iguanians & Sphenodon are similar) More substantial tongue projection evolved in several lineages: Salamandridae; Chioglossa & Salamandrina Plethodontidae; several groups All forms are lungless; Buccal floor freed from respiratory function (=buccal pump) & removes constraint on hyobranchium
Describe the typical feeding sequence of projectile tongue feeding in Caudates.
Typical feeding sequence in Caudata: 1. Tip of mandible often placed in contact with substrate 2. Muscle contraction raises skull 3. Contraction of the paired muscles draw hyobranchium (=hyobranchial skeleton or hyoid apparatus) forward; Tongue supported by hyobranchium; Pushes tongue out of mouth. 4. Tongue generally changes shape; Well defined ridge anteriorly, with central depression; Prey adheres to sticky secretions of tongue 5. Tongue retracted by contraction of separate muscle Net result: tongue protruded only a few millimeters from mouth
How does the typical feeding sequence of Caudates differ in Plethodontid Salamanders?
Plethodontid Salamanders
Most pronounced in bolitoglossines
Some project tongue up to half their body length
Same muscles are involved as in other caudate “minimal” projectile tongue feeding
Muscles and hyobranchium more greatly modified
Prey adheres to sticky surface of tongue and is drawn back into mouth
Feeding sequence takes only 4-6 milliseconds
Main components of projectile tongue: Y-shaped hyobranchial skeleton; Long, tapering epibranchial cartilages; Paired ceratobranchial cartilages; Basibranchial cartliage (Supporting base of tongue; tongue not attached to floor of mouth); & Specialized muscles: Subarcualis rectus I (Tightly coiled around epibranchials) & Retractor muscle
Describe Projectile Tongue Feeding in Anurans.
Most species feed via a projectile tongue
May be combined with lunging body toward prey
Tongue essentially flipped out of the mouth
Anterior end of tongue attached to floor of mouth;
posterior portion is free
Tongue supported by genioglossus muscles
Tongue projection not as rapid as salamanders Takes ~ 35-40 milliseconds
Not all anurans rely on projectile tongue; Rhinophrynus: Feeds on ants and termites (Relies on tongue protrusion) & Pipidae: Tongueless (suction feeding)
What is the feeding sequence of projectile tongue feeding in Anurans?
Feeding sequence:
- Genioglossus contracts & stiffens forming a stiff rod
- Submentalis muscle also contracts; Short, transverse muscle at front of mandible; Contraction causes muscle to bulge upward
- Submentalis pushes on stiffened tongue; Propels tongue upward and forward
- Free posterior end of tongue flipped forward and downward onto prey; Prey adheres to sticky tongue surface
- Contraction of hyoglossus muscle retracts tongue

Describe projectile tongue feeding in Chameleons.
Represents a clade within the Chamaeleonidae
Capable of projecting tongue ~1.5-2X their snout-vent length
Main components of projectile tongue:
Tip: external sticky pad and powerful circular muscle (=accelerator muscle)
Accelerator muscle wrapped around anterior extension (=processus entoglossus) of hyobrancial skeleton; Accelerator muscle constricts on processus entoglossus
Hyoglossus muscle attached to posterior end of tongue tip; At rest, loosely pleated behind tongue; Retracts tongue to mouth
What were the two different feeding environments mentioned in class?
What are the advantages and disadvantages of each?
Two feeding environments are Terrestrial and Aquatic.
Methods of feeding in aquatic and terrestrial environments differ
Advantages of aquatic feeding & disadvantages of terrestrial feeding:
- ) Food manipulation accomplished without much effort in aquatic environment & effort required in terrestrial
- ) Saliva not required for food lubrication in aquatic but required in terrestrial
Disadvantages of aquatic feeding and advantage for terrestrial:
1.) Predator movement generates pressure waves & moves prey away in aquatic but not in terrestrial
Define and describe suction feeding in aquatic environments.
Aquatic salamanders (adults&larvae), aquatic frogs, tadpoles, some turtles use suction feeding
Essentially Sucking/drawing food into mouth
Two main factors must be overcome: 1.) Initial inertia 2.) Water viscosity **Requires great deal of force
Involves negative pressure in the buccal cavity via expansion of buccal cavity
Generate enough pressure to draw prey into mouth
Must be rapid to prevent prey escape

Suction Feeding
Mouth opening usually small which allows directional suction;
EITHER 1.)** Unidirectional** flow of water through buccopharyngeal cavity; Only possible when gill slits present
2.) If no gill slits, depends on bidirectional flow
Define and describe unidirectional flow suction feeding in aquatic environments.
Aquatic Salamanders; Larval and highly paedomorphic salamanders possess gill slits
Two phases involved with suction feeding
- ) Expansive phase: Jaws open, hyoid apparatus drops, and buccopharyngeal cavity expands; Rapid flow of water into and through the buccopharyngeal cavity (negative pressure)
- ) Compressive phase: Rapid elevation of mandibles (=closing mouth), hyoid apparatus elevated; Water ejected through gill slits (positive pressure
Tadpoles: Employ different mode of suction feeding; Unidirectional flow of water & continuous suction feeding by continuous pumping of buccal cavity (not in bursts)
Define and describe bidirectional flow of suction feeding in aquatic environments.
What are the different ways this is made more efficient in Anurans, Turtles, and Tadpoles?
Bidirectional flow is when food is pumped into the mouth, but then the water must go back out of the mouth; less efficient because loss of prey item more likely
Anurans; Adult Pipid frogs; Xenopus and Pipa also use forelimbs to place food in mouth.
Turtles; Some aquatic turtles employ suction feeding; No gill or pharyngeal slits = bidirectional flow; Before opening mouth (=dropping lower jaw), hyoid is elevated in order to maximize the amount of negative pressure generated
Tadpoles; Water continuously passed across a filter; Most tadpoles feed on suspended phytoplankton or scrape algae from substrate; Alternating dropping and elevating the buccal floor (=floor of mouth) of buccal cavity moves water through system = buccal pump; Suspended food particles trapped by filter; Particle filtration takes place in pharyngeal cavity; Sieving through branchial filters or entrapment by mucus filaments (mucus entrapment); Mouth parts generally have several rows of small keratinized structures on oral disk surrounding mouth or labial teeth (labial tooth rows)
Explain in detail the suspention feeding by bidirectional flow in tadpoles.
What are the different mechanisms that have evoloved for terrestrial feeding?
Different mechanisms have evolved for terrestrial feeding
Major specialized mechanisms involved:
Tongue protrusion (including projectile tongue)
**Cranial kinesis; **squamates (particularly snakes!)
Constriction
Venom delivery
Akinetic skulls and nonprojectile tongue feeding
General characteristics are rigid skull and hinged mandible
Describe Akinetic Skull and Nonprojectile Tongue Feeding in Caecilians.
Compact and rigid skulls; Adaptation for burrowing; Some lineages have limited cranial kinesis
Well developed (relatively large), recurved teeth; Assists with prey capture and restraint/retention
Tentacle: Chemosensory function
Describe Akinetic Skull and Nonprojectile Feeding in Turtles.
Generally, heavily built skulls (Retained, primitive condition)
Absence of cranial kinesisis likely a secondary loss (=derived condition); Occurred early in turtle evolution
Extant taxa lack teeth; Upper and lower jaws covered with sheaths = rhamphothecae (Composed of keratin)
Jaws often modified for different diets
Broad crushing jaws for feeding on hard-bodied prey (=durophagous) like mollusks and crustaceans U.S. taxa: Graptemys, Malaclemys
Narrow jaws with sharp rhamphothecae for Slicing/dismembering soft-bodied prey; “chopping” U.S. taxa: Apalone, Chelydra
Sharp rhamphothecae & rearward motion of lower jaw; Primarily seen in testudinids; Herbivorous diet so rhamphotheca modified for slicing plant material
