Cetaceans Flashcards
Pakicetus
Primary land animals (Thewissen et al, 2001)
Pakicetus bones
Limb bones are osteosclerotic = aquatic habitats
Heavy bones provide ballast
They could stand in water, almost totally immersed, without loosing visual contact withthe air
What is the the involucrum in cetaceans?
The medial tympanic wall is inflated
What is the tympanic plate in cetaceans?
Thinning of the lateral tympanic wall
Artiodactyls walls
The median and lateral tympanic walls are more similar in thickness
Rodhocetus body
Is an Eocene whale that had short limbs with long hands and feet that were probably webbed.
It had a sacrum that was immobile with four partially fused sacral vertebrae
It possesses land mammal characteristics = evolutionary of land to sea
Thermoregulation
Aquatic environment is a heat sink
Large brain needs lots of heat- in built thermogenic system
Large appendages act as radiators
Do animals feel cold like humans?
Skin is innovated with temperature-sensing nerve cells
They have the ability to sense temperature
They respond to temperature stimuli
Thermal properties of water
Specific neat per unit volume X 3,400 that of air
Thermoconductivity is x25 that of air
Polar oceanic water temperature
Can get as cold as -2°C
Seawater in temperate or tropic temperature
Can drop as low as -1°C if you go deep enough below the surface
How do endothermic marine mammals deal with it?
One way of minimizing heat loss is to have a relatively low surface area-to-volume ratio:
A small amount of skin= across which heat is exchanged within the environment
Large volume of body tissue-which generates heat
Larger animals send to have lower surface area-to-volume ratios
What is blubber?
Excellent insulation in the form of fur or blubber
Animals that spend most their time in water rely on more blubber
Metabolic activity - killer whales
Basic metabolic rate vs body mass for killer whales
Killer whales have significantly higher metabolic rate than a terrestrial mammal with similar mass
Highlights of cetacean brains
Highly developed neocortex
High degree of foliation
High degree of folding associated with neocortex
Imitation behaviour
Important type ot social leaving that car readily lead stable cultures
Social motor imitation - study in dolphins
Demonstrated first by dolphins= allowed to see each other but not the trainers
The demonstrator dolphin was instructed to perform a behaviour
Then the imitator had to mimic the behaviour
Both dolphins performed the behaviour
Four challenges of whale vision
Pressure
Optic refraction of surrounding environments
Cold
Light levels
Snarks vision
Accommodation due to lens displacementnot distortion
Displacement may be achieved via intra ocular pressure changes
Achieved via axial displacement of the ocular globe using retractor/protractor muscles
Six facts about snark vision
Photoreceptors sensitivity is shifted towards Bluewave lengths
Vision is monochromatic
Tapetum are present
Highly vascularised
Thickened sclera and cornea
Large extrinsic ocular muscles
Oscine (songbird) birds and humpback wales
Use song complexity to assess male fitness, whereas the role of complexity in humpback whale song is uncertain owing to local population-wide conformity to one song pattern
Song patterns of humpback whales
Depends on where the live, with populations inhabiting different ocean basins normally singing singing quite distinct songs
They would sing a consistent song year after year
When do male humpback whales?
Sing while migrating to and from their breeding grounds, and when they are at the grounds themselves
Song is thought to be a form of sexual display/courtship, but it is not known whether its main purpose is to repel other males or to attract females
Males in same population
Produce the same song, which changes through time and all singers maintain the changes, implying that there is a cultural transmission and evolution as in some bird songs
Ocean basin
Songs across an ocean basin are broadly similar-differences increase with distance- but populations in different oceans separated by continents have apparently unrelated songs
Four main components of echolocation
Propagation
Focusing
Reception
Interpretation
What is focusing (melon)?
Low density lipids (oil filed) = acoustic lens
Similar density to surrounding water-less refraction
Fine adjustment of beam focus according to target distance
Is there a relationship between sound and prey capture? Miller et al (2004)
During foraging dives, sperm whales produce long series of regular clicks at 0.5-2s intervals / interspersed with rapid-click buzzes called ‘creaks’
Using rags that measured sound, depth and orientation to test whether the behaviour of diving sperm whales support the hypothesis that creaks are produced during prey capture
Sperm whales spent most of their bottom time within one or two depth bands, apparently feeding in vertically stratified prey layers
Predators and foraging decisions
Based upon sensory into about resource availability
Sperm whales employ a directed search behaviour by modulating their overall sonar sampling with the intention to exploit a particular prey later.
They forage opportunistically during some descents, well actively adjusting their acoustic gaze to track different pray
Whilst foraging within patches sperm whales adjust their clicking rate both to search new water volumes as they turn to match the price distribution
