Bat Eavesdropping

Raphael Arlettaz. R. Arlettaz, et al., “Effect of acoustic clutter on prey detection by bats,” Nature 414 (2001), pp. 742–745.

A mouse-eared bat (Myotis myotis) approaches and captures a cricket placed on the surface of a doormat. As the bat approaches the potential prey item, it reduces both its flight speed and the intensity of its echolocation calls. Echolocation does not prove useful in localizing the prey item in this context, as echoes from the cricket are masked by those from the doormat. Instead, in the face of acoustic clutter, these bats apparently eavesdrop on prey-generated sounds to pinpoint the location of their prey. The photoflash toward the end of the sequence allowed researchers to synchronize the audio and video recordings in each laboratory trial.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 11, “Foraging”; chap. 13, “Communication.” R. Arlettaz, G. Jones, and P. A. Racey, “Effect of acoustic clutter on prey detection by bats,” Nature 414 (2001), pp. 742–745.

Leaf-Cutter Ants Transport Leaves

Video © Tim Brown / Time-Science.com

A column of leaf-cutter ants (Atta sp.) ferries freshly cut leaves to their nest, where the leaves will be processed and inoculated with fungal hyphae and then serve as a substrate supporting the growth of the fungal gongylidia on which the ants feed. Mature leaf-cutter ant colonies often contain millions of workers, which are divided further by size into distinct subcastes, each performing specific functions within the colony. The smallest “minim workers” tend developing brood and the fungus gardens within the nest. Slightly larger minims called “minor workers” are an integral part of the foraging column, sometimes “hitchhiking” atop the leaves carried by larger “media workers,” and defending their burdened colony mates from attack by predators and parasitic phorid flies. Finally, “major workers” act as soldiers, guarding the nest and occasionally breaking trail or mandibulating large items into smaller pieces that can be transported by the media workers.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 10, “Cooperation”; chap. 11, “Foraging.” D. H. Feener, Jr., and K. A. G. Moss, “Defense against parasites by hitchhikers in leaf-cutting ants: A quantitative assessment,” Behavioral Ecology and Sociobiology 26 (1990), pp. 17–29.

Pigeon Foraging Behavior

Courtesy Luc-Alain Giraldeau

In addition to the distribution and abundance of food itself, information gleaned from conspecifics can have a pronounced influence on where individuals choose to forage. In some species, exacting information regarding the presence, location, and even the nature of food is communicated directly (as is the case in honeybees), while in others, information regarding food resources is acquired by observing others foraging. In this clip, pigeons (Columba livia) are seen joining others foraging in an array of food-containing trays (patches). Patch choice is not independent of the foraging location of others. But rather than distributing themselves evenly among potential patches, as predicted under the resource-matching rule, pigeons selectively join apparently successful foragers.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 11, “Foraging.” B. G. Galef, Jr., and L.-A. Giraldeau, “Social influences on foraging in vertebrates: Causal mechanisms and adaptive functions,” Animal Behaviour 61 (2001), pp. 3–15.

Producer/Scrounger Strategy

Courtesy Luc-Alain Giraldeau

Animals foraging as part of a group choose between searching for food on their own (producers) versus searching for opportunities to capitalize on food located by others (scroungers). The producer strategy generally results in a more variable return on foraging investment, as an individual searching for its own food may discover nothing, or alternatively, an abundance of food, while scroungers don’t obtain sole access to large finds, but at least get something for their effort. Thus, risk-sensitive foragers (those attending to variability in food abundance in choosing among foraging patches) are expected to adjust their foraging strategy according to their energetic state, adopting the risk-averse scrounger strategy when they enjoy a positive energy budget, and the risk-prone producer strategy when subject to a negative energy budget. The nutmeg mannikins (Lonchura punctulata) shown in this video clip do just that, and they can be seen manifesting both producer and scrounger strategies. Using the apparatus and paradigm depicted here, Luc-Alain Giraldeau and his collaborators have made important contributions to our understanding of social foraging.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 11, “Foraging.” G. M. Wu and L.-A. Giraldeau, “Risky decisions: A test of risk sensitivity in socially foraging flocks of Lonchura punctulata,” Behavioral Ecology 16 (2005), pp. 8–14.

Raven Problem-Solving

Courtesy Bernd Heinrich

Cognitive abilities of non-human animals are readily evident where animals adapt to novel challenges faced while foraging. Here, a common raven (Corvus corax) solves the problem of accessing a piece of meat suspended by a string from a branch, despite never having encountered a parallel foraging situation in nature and never having encountered string in any other context. Individual variation in the exact motor patterns employed in accessing the food, along with the ongoing failure of some individuals to solve the problem, suggests that the behavior is not genetically programmed, while the abrupt transition from failing at the task to reliably accessing the meat via progressively shortening the string suggests insightful problem solving rather than trial-and-error learning.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 5, “Learning”; chap. 11, “Foraging.” B. Heinrich and T. Bugnyar, “Testing problem solving in ravens,” Ethology 111 (2005), pp. 962–976.

Snowy Egret Foraging

Jack P. Hailman

A snowy egret (Egretta thula) trails behind a white ibis (Eudocimus albus), opportunistically foraging on material released as the ibis wades through the marsh. Snowy egrets feed on crustaceans, insects, and small fish. Adult snowy egrets have bright yellow feet that are thought to act as lures, drawing fish within reach of the foraging egret’s bill. Selection has favored the evolution of a variety of morphological characteristics and strategies that enhance the foraging success of ambush predators, including crypsis, the use of cover, and prey attractant lures.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 11, “Foraging.” J. A. Kushlan, “Feeding behavior of North American herons,” Auk 93 (1976), pp. 86–94.