Foraging morphology and behaviour. Week 3 Flashcards
Intended learning outcomes
- Describe morphological adaptations to foraging in marine mammals, and discuss these in relation to their terrestrial relatives
- Describe some of the various foraging behaviours and diets of marine mammals
Pinniped teeth
- Incisors (I), canines (C), premolars (P) and molars (M)
- Terrestrial carnivores have heterodont teeth
- Pinniped postcanines (P+M) are now homodont (similar shape)
- Pinnipeds have reduction in number of teeth
- Typical mammalian: 44 teeth
- Phocids 22-36 teeth; otarids 34-38 teeth; walrus18-24 teeth
Large variation in pinniped skull and tooth morphology reflect differences in foraging behaviour and diet
Pinniped foraging types
– Pierce (fish, squid): capture and swallow
– Grip and tear (fish, birds, seals): capture, tear and swallow large prey
– Filtering (invertebrates/krill): filter prey through teeth (like baleen)
– Suction (invertebrates, squid, fish): suck prey in without using teeth
Pinnipeds often use a combination of types, depending on prey!
- spotted seal using teeth and claws
- Leopard seal suction feeding on fish and tearing fur seal
Example: using tags to study pinniped foraging behaviour
- Possible information from tag
– Time, location, surfacing and haul-out patterns
– Depth, acceleration, tilt, etc
– Acoustics, heart rate, respiration, etc
– Water temperature, salinity, chlorophyl content - Trade-offs
– Deployment of tag can be difficult
– Size of tag relative to animal size
– Battery life vs. amount of data
– Duration of deployment (hours to years)
– Need to retrieve tag or not?
Southern elephant seal foraging
- Circum-Antarctic distribution; 0.5-1mill. Animals
- Spend more than half a year at sea foraging
- Dive constantly; 20 min dives; 1000 m (record >2000 m)
- Feed on squid and fish, which they locate by sight (prey bioluminescence) and highly sensitive vibrissae
Mysticete foraging types
- Gulp/lunge feeding on schooling fish and krill (rorquals)
- Skim feeding on copepods and krill (right whales)
- Suction feeding on benthic invertebrates (grey whale)
Example: Humpback whale foraging behaviour
- Friedlander et al 2009
- Echo-sounders to track sand lance (prey)
- Deploy D-TAG on humpback whales
- TrackPlot program (Ware et al 2006)
- https://www.youtube.com/watch?v=40e3UvQAfIs
Humpback whales follow the diurnal rhythm of their prey (sand lance)
Odontocete foraging types
- Foraging types (single, or combination)
– Grip/tear (e.g. orcas)
– Pierce (e.g. most dolphins and porpoises)
– Suction (e.g. narwhal, beaked, pilot and sperm whales) - Foraging behaviours
– Individually or in groups (e.g. porpoises vs. oceanic dolphins)
– Pelagic or deep-diving (e.g. dolphins vs. beaked whales)
– Ecotypes (coastal-oceanic, stationary-migratory) - Great diversity of behaviours and local adaptations!!
– Bottlenose dolphin circle feeding (1:40 min)
dolphin beaches for fish (2:50 min)
Odontocete foraging types
- Foraging types (single, or combination)
– Grip/tear (e.g. orcas)
– Pierce (e.g. most dolphins and porpoises)
– Suction (e.g. narwhal, beaked, pilot and sperm whales) - Foraging behaviours
– Individually or in groups (e.g. porpoises vs. oceanic dolphins)
– Pelagic or deep-diving (e.g. dolphins vs. beaked whales)
– Ecotypes (coastal-oceanic, stationary-migratory) - Great diversity of behaviours and local adaptations!!
– Bottlenose dolphin circle feeding (1:40 min)
dolphin beaches for fish (2:50 min)
Summary: variation in baleen and teeth
- Rorquals (fin whales)
– Short baleen plates, throat grooves, well-developed coronoid process, elastic tongue - Right whales
– Long baleen plates, arched rostrum, long lower lips
*Grey whale
– Short white coarse baleen plates, semi-arched rostrum
- Odontocetes
– Homodont teeth, large variation in number and function of teeth (and some species without teeth)
Sirenia foraging behaviour
- Feed on seagrass (and invertebrates) in shallow waters
- Manatees both marine and freshwater; dugongs mainly marine
- Dugongs are strictly bottom feeders; manatees can also forage in the water column and at the surface
- Eyesight is poor, so locate food with smell and vibrissae
- Semi-nomadic and can travel large distances in search for food
and between winter and summer areas, when water gets too cold - Dugongs have tusks that erupt in males during puberty
Sirenia foraging behaviour
- Feed on seagrass (and invertebrates) in shallow waters
- Manatees both marine and freshwater; dugongs mainly marine
- Dugongs are strictly bottom feeders; manatees can also forage in the water column and at the surface
- Eyesight is poor, so locate food with smell and vibrissae
- Semi-nomadic and can travel large distances in search for food
and between winter and summer areas, when water gets too cold - Dugongs have tusks that erupt in males during puberty
Sirenia foraging morphology
- Some similarities to terrestrial relatives hyrax and elephant
- Tooth row with flat “herbivore” teeth for grinding sea-grass
- Dugong rostrum and mandible oriented downwards so strictly bottom feeder
- Dugongs have tusks that erupt in males during puberty (mating)
