Ecological and social drivers of neighbor recognition and the dear enemy effect in a poison frog

Abstract

Navigating social relationships frequently rests on the ability to recognize familiar individuals using phenotypic characteristics. Across diverse taxa, animals vary in their capacities for social recognition, but the ecological and social sources of selection for recognition are often unclear. In a comparative study of two closely related species of poison frogs, we identified a species difference in social recognition of territory neighbors and investigated potential sources of selection underlying this difference. In response to acoustic playbacks, male golden rocket frogs (Anomaloglossus beebei) recognized the calls of neighbors and displayed a “dear enemy effect” by responding less aggressively to neighbors’ calls than strangers’ calls. In contrast, male Kai rocket frogs (Anomaloglossus kaiei) were equally aggressive to the calls of neighbors and strangers. This species difference in behavior is associated with key differences in reproductive ecology and characteristics of territories. Golden rocket frogs defend reproductive resources in the form of bromeliads, which is expected to create a threat asymmetry between neighbors and strangers favoring decreased aggression to neighbors. In contrast, Kai rocket frogs do not defend reproductive resources. Further, compared with Kai rocket frog territories, golden rocket frog territories occur at higher densities and are defended for longer periods of time, creating a more complex social environment with more opportunities for repeated but unnecessary aggression between neighbors, which should favor the ability to recognize and exhibit less aggression toward neighbors. These results suggest that differences in reproductive ecology can drive changes in social structure that select for social recognition.

Dynamic changes to signal allocation rules in response to variable social environments in house mice

“…Another possibility is males respond differentially to the urine of males with whom they have established relationships versus unfamiliar novel males. In many territorial species, familiar neighbors reduce aggressive behaviors and signaling effort toward familiar individuals known as the “dear enemy” effect (Booksmythe et al, 2010; Briefer et al, 2008; Christensen & Radford, 2018; Tumulty & Bee, 2021; Zorzal et al, 2021). The dear enemy effect is well-documented across vertebrate species, and is thought to lessen the costs of territorial defense (Tumulty, 2018).…”

Identity signaling, identity reception, and the evolution of social recognition in a Neotropical frog

“…Golden rocket frogs call from and defend territories in giant tank bromeliads, whereas Kai rocket frogs call from and defend territories on the forest floor (Bourne et al 2001;Kok et al 2006;Pettitt et al 2018Pettitt et al , 2020Tumulty and Bee 2021). Advertisement calls typically consist of a series of three pulses (range 1-6) for golden rocket frogs or two pulses (range 1-2) for Kai rocket frogs (Figs.…”

“…In the context of the dear enemy effect, identity reception likely evolved in response to the ecological and social conditions of golden rocket frog territories. Golden rocket frogs defend stable reproductive resources in the form of bromeliads that contain arboreal pools of water where males care for eggs and tadpoles (Bourne et al 2001;Pettitt et al 2020;Tumulty and Bee 2021). The defense of these limited resources may produce a threat asymmetry between established neighbors, who already possess resources of their own, and strangers, who may be nonterritorial "floaters" looking to establish a territory of their own (Tumulty and Bee 2021).…”

“…Bromeliads naturally grow in spatially clumped distributions, putting males in close proximity to neighbors. Compared with Kai rocket frogs, golden rocket frogs defend territories at higher densities, with neighbors often less than 5 m apart, and males often defend the same territories for multiple years (Tumulty and Bee 2021). This social environment has presumably selected for the ability to habituate to specific neighbors' calls, allowing males to both avoid the costs of repeated but unnecessary aggression with established neighbors and also aggressively defend their territories from intrusion by strangers.…”

“…Neighbor recognition and the dear enemy effect likely evolved in golden rocket frogs in response to ecological and social conditions associated with breeding in spatially clumped bromeliads ("phytotelm breeding"), which puts males in closer proximity for longer periods of time than does the terrestrial reproductive ecology of Kai rocket frogs (Tumulty and Bee 2021). Kai rocket frogs defend territories on the forest floor and transport tadpoles from terrestrial egg clutches to pools of water (Tumulty and Bee 2021). Terrestrial breeding is ancestral in the genus Anomaloglossus (Fig.…”