Evolution of Feeding Behaviour Flashcards
Search image
Tinbergen observed that when a new type of caterpillar appeared in woodlands, songbirds rarely brought it to their nests. But once a few had been located, the birds collected them at a greater rate.
The birds had come to recognise the caterpillars and had formed a search image.
Testing the search image hypothesis
Pietrewicz and Kamil used operant conditioning to investigate search images in captive blue jays.
Blue jays were shown slides of cryptic moths of either the same or 2 different species.
The birds’ improved when presented with one species, but not when given both species.
Finding food by smell in skunks
Striped skunk is a nocturnal forager and finds food by odour. Young skunks were allowed to forage in an outdoor enclosure. Food was found at greater and greater distances as they gained experience. Maximum distance over which food is detected also increases.
Lizard foraging: evolutionary history
Vision/ambush evolved twice, in 8 species. Olfaction/searching evolved 3 times in 8 species. Evolved later than vision.
Social foraging
Social Insects:
Groups composed of related individuals
Cooperation favoured by kin selection. Deliberate communication with nestmates.
e.g. waggle dancing, direct leading, pheromone trails.
Other group living animals:
Groups normally composed of mostly unrelated individuals
Cooperation not favoured by kin selection. Incidental communication with conspecifics.
e.g. observing location of successful foragers
Other foraging advantages for groups:
Take prey much larger than themselves
e.g.wolves take moose; army ants large arthropods/other insect colonies.
The Waggle Dance:
Karl von Frisch
Round dace (food<50m) Figure of 8 dance (food>50m)
Angle and duration of waggle dance
Angle from sun is the angle from the vertical in the combs.
In a ‘fan test’ Karl von Frisch trained scout bees to a feeder at F.
He then put out feeders of equal attractiveness at all 7 stations and counted the recruits.
More arrived at the advertised location, F, than other locations.
Scout bees trained to a feeder 750m from hive.
After waggle dance recruits went most often to feeders close to 750m (all feeders in same direction).
Natural combs are vertical.
Honey bee foragers will dance on horizontal combs, orienting to a directional light source instead of gravity.
By removing directional light from horizontal combs the directional information in the dances is removed.
It is then possible to compare the success of bees with informative dances, to bees with non-informative dances.
A larger proportion of recruits come to the advertised site when combs are vertical.
Recruits locate advertised site more easily when combs are vertical.
Honeybee distance measuring mechanisms
Tunnel shown is 1 x 1cm random pattern.
The tunnel can also have 1cm parallel stripes running lengthwise.
The image motion hypothesis predicts that foragers in Experiments 2 and 4 are less likely to make round dances, which normally indicate distances of less than 50 metres. The data support this prediction.
Srinivasan et al. 2000. Science 287: 851-853.
Benefits of waggle dance
By following dances, foragers don’t find flowers faster. But they find better quality ones, as only scouts finding high quality flowers dance.
Fitness benefits of waggle dance
Honeybee colonies achieve fitness in winter but not summer, through dancing.
Social foraging in ospreys
Informed birds find fish faster than naïve birds. If they didn’t, there would be no benefit in receiving information.
Swallows
Barn swallows nest in colonial aggregations
Unsuccessful foragers don’t follow successful ones because their prey (insects) move around too quickly
