Frogs belong to the order Anura, and comprise a diverse, highly successful group of animals with species on all continents except Antarctica. The greatest abundance of frogs can be found in tropical rainforests, where they exploit the high productivity of their environment.
Anurans perform a wide range of social behaviors – however, a distinction must be drawn between displaying these behaviors and being a social animal. Social behaviors can exist in aggressive as well as friendly interactions. This article explores the question: are frogs social?
Communication
Anurans utilize various methods of communication, which are vital in social interactions. For example, male Trinidad stream frogs (Mannophryne trinitatis) communicate using color changes, turning black while they are calling and light brown while foraging. Nocturnal frogs such as the bicolor treefrog, Phyllomedusa bicolor, utilize their coloration in recognizing conspecifics in low-light conditions.
Studies have found that the size of a frog and its movement can also be used by conspecifics to determine their responses – this demonstrates that other elements of visual communication are at play. Inflation of the vocal sac during calling is another visual signal that female frogs in particular respond to.
Auditory communication is used between frogs. Vocalizations can function to attract mates, and the female Malaysian treefrog, Polypedates leucomystax, taps her feet to help males locate her. This is not the only example of females using their feet to communicate: female dyeing poison dart frogs, Dendrobates tinctorius, place their forelimbs on the back or head of the male to initiate courtship. Vocalization is also used in the context of aggressive calls, which are used to maintain territories and warn off other males.
Social Ecology
The social structure of many frog species tends to follow a similar pattern. Males and females each defend their own territory, with vocalizations and social behaviors typically reserved for the defense of these territories, or for courtship and mating. This can be seen clearly in the rocket frog, Colostethus inguinalis.
However, there are a few exceptions to this rule, in which vocalizations are not used solely for territoriality or courtship. For example, female Cope’s gray treefrogs will use auditory cues from breeding aggregations to navigate to them, gaining information about the location and the timing of the breeding event. Male Pacific treefrogs, Hyla regilla, have been found to respond to hearing the calls of conspecifics by altering the timing of their own calls. This behavior not only reduces interference between calls but demonstrates the ability of this species to respond to social cues and adjust its actions accordingly.
Individual characteristics of a species may affect their sociability. Larval green and gold bell frogs, Litoria aurea, are more attracted to conspecifics when they are smaller in size. As they grow, they become more independent, most likely due to the decreasing risk of predation at a larger size.
Agonistic Behavior
Many of the social behaviors shown by anurans revolve around reproduction. Some species perform ‘explosive breeding’ in which males rapidly scramble over one another, attempting to gain access to females. The competition between males during this time is fierce. Similarly, prolonged breeders display agonistic territorial behaviors towards other males. During this time, individuals attempt to maintain distance between one another.
The Trinidad stream frog, Mannophryne trinitatis, displays a variety of agonistic behaviors towards conspecifics – for example, females perform territorial displays and will pounce upon and wrestle intruders. Individuals of this species definitely prefer their own space, and only associate with each other for courtship and mating.
Conclusions – Are Frogs Social?
Overall, frogs are not especially social animals. They typically prefer their own space and maintain strict territories, only gathering together at specific sites for reproductive purposes. Throughout the remainder of the year, frogs of both sexes display agonistic behaviors towards one another in order to keep adequate distance between them. One exception to this is that larval individuals may reside in groups for safety, but this sociality is lost once they have undergone metamorphosis.
