PSY 2364 Animal Communication

Transcription

1 PSY 2364 Animal Communication Jumping Spider (Phidippus putnami) Peacock Spider (Maratus speciosus) Peacock Spider (Maratus mungaich) Jurgen Otto Jurgen Otto Signal: behavior or structure that alters the behavior of another animal, which evolved because of that effect, and is effective because the receiver s response has also evolved. If one stag pushes another stag, it is not a signal; but if one roars and the other retreats, it is a signal. Cue: behavior or structure or feature of the environment that can be used by an animal as a guide to future action. A mosquito searching for a mammal to bite will fly upwind if it detects CO 2. The CO 2 is a cue for the mosquito, but it is not a signal by the mammal. 1

2 Index: a signal whose intensity is related to the quality it signals, and which cannot be faked. Bright colored skin patches (wattles, combs) are displayed by birds during courtship, and these signals may serve as indices of parasite resistance. Weapons (e.g. horns in goats, sheep, deer) are displayed during aggressive interactions. Index: a signal whose intensity is related to the quality it signals, and which cannot be faked. Bright colored skin patches (wattles, combs) are displayed by birds during courtship; these may serve as indices of parasite resistance. Weapons (e.g. horns in goats, sheep, deer) are displayed during aggressive interactions. Handicaps Handicap: A signal whose reliability is ensured because its production is costly; the signal may be difficult to produce or have costly consequences. Peacock tail feathers Male stalk-eyed flies have longer eye stalks; females prefer males with large eye span Zahavi (1975) Information and deception Not all signals involve sharing information for mutual benefit. Signals may be transmitted to manipulate others, including members of the same species and even members of the same family. Male bluegill sunfish mature at 2-3 years of age, but have not yet acquired full size. Territorial males do not drive them off as rivals because they resemble females ( female mimicry ). Deception occurs when these young males fertilize the eggs. Information and deception During aggressive interactions animals sometimes make themselves appear larger than they really are. Siamese fighting fish extend their fins when swimming alongside an opponent and raise their gill covers in face-to-face encounters. These actions make them look larger than they really are. Limits on deception If it is advantageous to appear larger than you actually are, natural selection will favor the trait and animals will continue to exaggerate the display. 2

3 Limits on deception But physical limitations prevent animals from appearing substantially larger than they really are. Once this limit is reached, all members of the population share the trait of size exaggeration and the deception becomes reliable signaling. Calls of young birds Chicks pip a small hole through the inside membrane of the egg to provide an air bubble, start breathing and make vocal sounds. Chicks may synchronize their time of hatching based on the sounds made by their brothers and sisters. Parent birds anticipate hatching by listening to the peeping sounds made by chicks 1-2 days before hatching. Calls of young birds Cross-species variation in parental investment Precocial species need little parental care Altricial species need lots of parental care No parenting invertebrates Begging calls Parent birds of altricial species are stimulated to feed their offspring not only by brightly coloured gape patterns flashed at them by hungry young, but also by begging cries. of need for food Food provision is critical to a young bird s survival. The hungrier they are the greater the intensity of begging (honest signalling). of need for food But why don t they always beg at maximum intensity (dishonest signalling)? Nest parasites (e.g., European Cuckoo) Begging intensity Begging intensity maximum intensity Need for food Need for food 3

4 Gape color mimicry in cuckoos Cost-benefit analysis Begging is beneficial (stimulates food provision; well-fed chicks more likely to survive). Begging sounds induce parents to bring more food to the nest. Studies of Pied Flycatchers have shown that when one parent hears (tape-recorded) begging calls from the vicinity of the nest, they bring more food than the other parent (who doesn t hear them). Cost-benefit analysis Begging is costly (energy required to make sounds, increased risk of nest predation) Artificial nests are more likely to experience predation if tape recordings of begging sounds are played. Ground nesting birds are more susceptible to predation than tree nesters. Chicks raised in tree nests make louder begging sounds; those raised in ground nests use higher frequencies that do not travel as far. Cost-benefit analysis Trade-off between cost and benefit depends on the circumstances: a hungry chick benefits more from begging than a well-fed chick. The cost is the same, so the optimal course of action is to adopt the strategy of honest signalling (beg in proportion to hunger level). Predation may cost the chick its life, but also the lives of its siblings. Begging intensity is higher in brood parasites (European Cuckoo, Brown-headed Cowbird) that are unrelated to their host. Alarm calling in chickadees "Chick-a-Dee" Calls The number of syllables and acoustic structure of these syllables is highly variable among different "chick-a-dee" calls. Some of this variation apparently communicates information about individual and flock identity. This call is also used to communicate about predators, some of the acoustic variation also serves to code information about the type or level of threat of the predator being mobbed. 4

5 Chickadee alarm calls encode information about predator size and risk. Alarm calling in chickadees Templeton C N, and Greene E PNAS 2007;104: by National Academy of Sciences Alarm calling in chickadees Alarm calls in Tufted Titmouse Chickadees often form mixed flocks with other species of small song birds (especially in winter). Recent research suggests that other species of birds in the flock eavesdrop on chickadee mobbing / alarm calls and respond to the perceived threat level. Mean duration (±standard error) of mobbing responses (in seconds) of tufted titmice responding to raptors and controls during 6-min presentation periods. When presented with raptors of varying size, the number of total D-notes uttered per titmouse in the first 2 min of the trial period decreased with increasing body length of raptors. Courter J R, and Ritchison G Behavioral Ecology 2010;21: The Author Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. For permissions, please journals.permissions@oxfordjournals.org Courter J R, and Ritchison G Behavioral Ecology 2010;21: The Author Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. For permissions, please journals.permissions@oxfordjournals.org 5

6 Bar graph showing the mean time (±standard error) before tufted titmice returned to normal feeding behavior after playback of chick-a-dee calls previously given to a small raptor (eastern screech-owl), a large raptor (red-tailed hawk), and a control (American robin mobbing calls). Social Eavesdropping hypothesis Beecher et al. (2006) found that young song sparrows learned more songs from adult song tutors they overheard singing with another bird ( eavesdropping ) compared to adult song tutors with whom they interacted socially ( direct interaction ). Courter J R, and Ritchison G Behavioral Ecology 2010;21: The Author Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. For permissions, please journals.permissions@oxfordjournals.org Juvenile male song sparrows approach playback speakers broadcasting two birds singing interactively more than they do for solo song or control playback trials (p < ). Elephants Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Proboscidea Family: Elephantidae Genus: Elephas Species: maximus Templeton C N et al. Proc. R. Soc. B 2010;277: Asian Elephant 2010 by The Royal Society An Asian Elephant Imitates Human Speech Angela S. Stoeger, Daniel Mietchen, Sukhun Oh, Shermin de Silva, Christian T. Herbst, Soowhan Kwon, W. Tecumseh Fitch, An Asian Elephant Imitates Human Speech, Current Biology, Available online 1 November 2012) 6