|Animal Cognition and Culture|
|(revised 30 October 2000)|
Definitions | Ant Fossils | Ant Brains | Ant Agriculture | Cognition in Bees | Jumping Spiders
Vocal Imitation in Birds | Animal imitation
is the scientific study of animal behavior, especially as it occurs in
a natural environment. An animal
is any multicellular organism of the kingdom Animalia, differing from plants
in certain typical characteristics such as capacity for locomotion, nonphotosynthetic
metabolism, pronounced response to stimuli, restricted growth, and fixed
Oldest known ant fossils top
Fossilized ants have been found preserved in amber, but exactly when they evolved has been uncertain. The only morphological character that separates ants from other Hymenoptera (bees and wasps) is the presence of the metapleural gland above the hind leg. This produces antibiotics to keep the brood clear of infection in the humidity of the nest, and communication by gland secretions may have been necessary for the evolution of eusocial behaviour. The oldest fossil suspected to be an ant could not be confirmed as such because the gland was not visible. Four more specimens have now been found, with a clear gland, preserved in amber some 92 million years ago. This is about 50 million years older than previous confirmed specimens, and suggests that ants evolved about 130 million years ago in the Early Cretaceous.
D Agosti, D Grimaldi & J M Carpenter. Oldest known ant fossils discovered
(Scientific Correspondence). Nature 391 (1998): 447.
Retinotopical Storage of Visual Information in Ants top
Judd and Collett (Sussex Centre for Neuroscience, UK) report a study of the visual guidance system of ants. Under some circumstances, Diptera (two-winged insects) and Hymenoptera learn visual shapes retinotopically, only recognizing a shape when it is viewed by the same region of retina that was exposed to it during learning. One use of such retinotopically stored views is in guiding an insect's path to a familiar site. The authors report that wood ants take several "snapshots" of a familiar beacon from different vantage points. An ant leaving a newly discovered food source at the base of a landmark performs a tortuous walk back to its nest during which it periodically turns back and faces the landmark. The ant, on revisiting the familiar landmark, holds the edges of the landmark's image steady at several discrete positions on its retina. These preferred retinal positions tend to match the positions of landmark edges that the ant captured during its preceding "learning walks". The methodology in this investigation involved first training ants to distinguish an upright and inverted cone, followed by fine-grain analysis of the approaches of individual ants towards cones and related borders.
QY: S.P.D. Judd, Sussex Centre for Neuroscience, School of Biological
Sciences, Brighton BN1 9QG, UK. (Nature 16 Apr 98 392:710) (Science-Week
8 May 98)
The Evolution of Agriculture in Ants top
Fungus farming by ants of the tribe Attini apparently originated in the early Tertiary period (70 to 3 MYA) and thus predates human agriculture by approximately 50 million years. During its extensive evolutionary history, this symbiosis between "attine" ant farmers and their fungal cultivars has acquired an astonishing complexity involving, among other things, secretion of antibiotic "herbicides" to control weed molds and elaborate manuring regimes that maximize fungal harvests. Of the over 200 known extant attine ant species, all are obligate fungus farmers. Cultivars are propagated vegetatively as clones within nests, and between parent and offspring nests. In the few studied cases, the foundress ant queen carries in her mouth a pellet of fungus from the origin nest that she uses to start her own garden. This mode of propagation has suggested the long-standing hypothesis that the fungi of attine ants are ancient clones that have strictly coevolved with their hosts.
U.G. Mueller et al (Science 281 (25 Sep 98): 2034) now report an analysis of the evolutionary history of this ant-fungi symbiosis as revealed in phylogenetic and population-genetic patterns of 553 cultivars isolated from the gardens of relatively primitive fungus-growing ants. The authors report these patterns suggest that fungus-growing ants succeeded at domesticating multiple cultivars, that the ants are capable of switching to novel cultivars, that single ant species farm a diversity of cultivars, and that cultivars are shared occasionally between distantly related ant species, probably by lateral transfer between ant colonies.
Contact: Ted R. Schultz <email@example.com>
Cognition in bees top
Dukas, R. and Real, L.A. (1993). Cognition in bees: From stimulus reception
to behavioral change," in Papaj, D.R., and Lewis, A.C. (eds.). Insect
Learning: Ecological and Evolutionary Perspectives. NY: Chapman &
Hall, pp. 343-373.
26 May 1998
A recent observation floating around the arachnology world is that salticids (jumping spiders) have some interesting cognitive abilities, in addition to an extraordinary good eyesight. They can see a prey item, and jump to where the prey will be, instead of jumping at where it saw the prey, a feat requiring reasonably complex calculations.
Contact: Kelly C. Kissane
Collaborative mimickry in blister beetle larvae
John Hafernik and Leslie Saul-Gershenz have studied the strategies that blister beetle larvae in the Mojave desert use to gain entry into bees' nests. Large numbers of the larvae cluster into a shape that vaguely resemble a bee and -- possibly with the use of pheromones -- attract a male. They cling to him to be taken to the female, who takes them into her nests, where they feed on her eggs and young.
"By first attaching to a male bee, the larvae have access to multiple females and, subsequently, the multiple nests of each female," said Dr Saul-Gershenz. Dr Hafernik added: "Until now, no other insect has been known to use co-operative behaviour to mimic other species."
They tested for olfactory cues by placing models of the larval groups near real aggregations. The female carries the larvae in to the nests "The male bees ignored the models completely but hovered or tried to land on the real groups of larvae even before they were formed into a bee-like mass," said Dr Saul-Gershenz. "The larvae are probably emitting a bee-like pheromone to attract males, and another chemical cue to form aggregations."
See BBC news article; the research was published in Nature in April/May 2000.
Vocal imitation in birds top
In songbirds, a network of brain regions are apparently dedicated to the learning, production, and perception of song, and there are indications that the sizes of these regions correlate with the capacity for song learning and production. The Australian zebra finch memorizes song material from kindred birds ("social tutors") during the period 20 to 60 days after hatching, begins song-like vocalization at 30 to 45 days of age, and by 90 days of age, the song pattern is stereotyped.
Ward et al. (1998) report that in male zebra finches individual differences in region volume and neuron number in two song-related brain regions showed positive correlations with differences in the number of song-syllables accurately copied. Since previous work has shown that volume and neuron number of these regions are not regulated by song learning, the authors suggest the correlations indicate that naturally occurring variations in neuron number constrain how much song material can be copied or reproduced, with variation in the number of song-related neurons possibly reflecting differences in cell production, cell specification, or cell survival. (Proceedings of the National Academy of Science. US, 3 Feb 98.)
Contact: K.W. Nordeen <firstname.lastname@example.org>
Jarvis et al. (2000) report on a study of behaviorally driven gene expression in hummingbirds; see abstract.
Al Cheyne suggests animals are unable to imitate. Young chimpanzees, whose sophisticated brains make them a primary candidate for imitative learning, do not appear to learn how to fish termites through imitation. The young chimps spend a considerable amount of time observing adults termiting, yet after getting the idea it is possible to get hold of the ants, they appear to learn the actual techniques by trial and error. "The combination of emulation and trial and error is a very powerful and robust strategy," he writes, "and raises questions in my mind about why imitation developed in humans at all" (November 13, 1998). Cheyne uses Tomasello's distinction between emulation (sharing of ends) and imitation (sharing of means): seeing another obtain a desirable goal leads to emulation to reach the same goal, but it may not lead to imitation in attaining this goal.
John Skoyles objects that the existence of mirror neurons (neurons that respond perceptually to actions they carry out) argues that the motor part of the brain is set up to imitate (Gallese et al. 1996 and Rizzolatti et al. 1996). A nonhuman primate seeing another do something automatically activates the neurons in their own brain that might carry out the same action.
Imitation, Cheyne speculates, may have evolved in humans to cement human relationships through precise mimetic rituals that could only be learned through precise imitation. This seems an overly restrictive hypothesis; imitation of actions may also have been extremely useful in toolmaking, which is nearly incommunicable in words and depends on precise techniques.
Gallese, V., Fadiga, L., Fogassi, L. & Rizzolatti, G. (1996). Action recognition in the premotor cortex. Brain 119: 593-609.
Rizzolatti, G., Fadiga, L., Gallese, V. and Fogassi, L. (1996). Premotor cortex and the recognition of motor actions. Cognitive Brain Research 3: 131-141.
Contacts: Al Cheyne <email@example.com>
John Skoyles <firstname.lastname@example.org>
© 1998 Francis F. Steen, Communication Studies, University of California, Los Angeles