ForagingForaging behaviorsbehaviors of of dolphins;an example of dolphins;an example of

beach huntingbeach huntingin Monkey Mia-Australiain Monkey Mia-Australia

IntroductionIntroduction

lobtail and bubble net feeding in humpback whales

bird-associated foraging and lunge feeding by minke whales

cooperative hunting and strand feeding by killer whales

Humpback dolphins push fish onto exposed sand banks at low tide and surge partially onto the banks to catch them

But what about But what about bottlenose dolphins bottlenose dolphins

((Tursiops truncatusTursiops truncatus) ?) ?

« strand-feeding » bottlenose dolphins in the southeastern United States

bottlenose dolphins, in the southeastern United States, the Colorado River Delta and Portugal ,use estuarine mud flats in order to hunt

...but there are both inter- and intrapopulation variability.

An example of beach hunting,An example of beach hunting,a rare foraging behavior, a rare foraging behavior,

by wild bottlenoseby wild bottlenosedolphins (dolphins (Sergeant and alSergeant and al.,2005).,2005)

Cape Peron, Peron Peninsula, Shark Bay, Western Australia

13 distinct foraging tactics

Beach hunting frequent fast swims in shallow water , creating a trail

of water off the dorsal fin, as dolphins chase individual fish parallel to and then onto the beach surface.

“partial beaching”

surging out of the water onto the beach with the ventrum touching the substrate FREQUENTLY

“full beaching” the dolphin emerges almost completely out onto thebeach OCCASIONNALY

four adult females and their offspring.

Cooperative and coordinated foraging was not observed

incoming tides and high tides, stranding risk lower during this time

dolphins forage individually, chasing singular prey for hundreds of metres parallel to and onto the beach.

Some dolphins are more specialized in beach hunting than other dolphins...

One female X:more time in shallow beach habitats, specializes in beach hunting higher success rate more solitary.

Another female Y :Less time in shallow beach habitats, specializes in another foraging tactic lower success rate more social.

=> dolphins overlapping in range can partition niche use, and may also show that once a dolphin learns one tactic it is not limited to that tactic alone.

The learning of calvesThe learning of calves

No calves were ever observed full beaching or definitely catching fish while beach hunting.

Although beach hunting has been observed in one calf in the first year, full beaching was not observed for at least the first 5 years.

=>complete development of beach hunting takes longer than other tactics, possibly because its complexity requires lengthy learning periods and (or) because calves are continuing to develop physically

• In spite of the presence of mother/calf associations, mothers were never observed attending to their calves or altering their foraging behavior in response to calf presence during beach hunting, presenting no evidence for teaching.

• Full beaching is a late-developing behavior compared with the majority of foraging behaviors used in Shark Bay

• Complex foraging in Shark Bay bottlenose dolphins may help explain their unusually long dependency periods (3– 6 years) and the sizable overlap between independent foraging and nursing

ConclusionConclusion

Beach hunting corresponds with tidal state and habitat use, develops later than other foraging behaviors, does not occur strictly within matrilines, and may involve social learning (but not teaching)

The challenge or even danger of becoming stuck on the beach is consistent with the fact that beach hunting occurs more during incoming tide, which could lower stranding risk

Thanks for your attentionThanks for your attention