Memory of conspecifics in male salamanders Plethodon cinereus: Implications for territorial defense

Abstract

We investigated how exposure duration (time that two individuals initially interact) and separation interval (time between the initial interaction and a subsequent interaction) affect recognition memory of conspecifics in male red-backed salamanders Plethodon cinereus. Previous studies have demonstrated that this species aggressively defends territories. We recorded aggressive behavior to assess recognition memory, because aggression is more intense toward previously unencountered individuals compared to previously encountered individuals in this species. We found that with 15-min exposures and 5-day separation intervals, focal males did not spend significantly more time threatening ‘unfamiliar’ intruders than ‘familiar’ intruders. After either 8-hour exposures and 5-day separation intervals and 5-day exposures and 5-day separation intervals, focal males spent significantly more time threatening unfamiliar intruders than familiar intruders. These results suggest that male red-backed salamanders can remember familiar conspecifics (e.g., territorial neighbors) after at least an 8-hour exposure duration and that memory persists at least as long as 5 days. After 5-day exposure and 15-day separation intervals, we found no significant difference in aggressive behavior toward familiar and unfamiliar intruders. Long separation intervals (15 days) may lead either to loss of memory of previously familiar individuals or, alternatively, aggressive reassessment of individuals as only a change in behavior indicates positively that memory has occurred. Thus, variance in territorial defense within an individual may depend on its ability to recognize conspecific males.

Opponent familiarity and contest experience jointly influence contest decisions in Kryptolebias marmoratus

“…These changes in estimated fighting ability modify individuals’ anticipated fighting costs and therefore their contest decisions. Pairs of contestants that have fought previously can also recognize each other and use the outcome of their previous interaction to settle their future conflicts (individual recognition [ 11 - 13 ]). By not fighting opponents to which it has recently lost, an individual can avoid the unnecessary costs of contests that it has a very low chance of winning.…”

Memória e socialidade: como o reconhecimento individual afeta formação de grupos

“…In individual recognition (IR), the individual doing the recognition (the receiver) needs to be able to (i) perceive and learn a certain phenotypical trait (known as cue) of the individual being recognized (the emitter), and (ii)to distinguish that trait from those of other conspecifics (Thom and Hurst 2004) , which implies a sophisticated sensory and memory system. Some degree of IR has been demonstrated in several different animal groups, including mammals (Briefer (Akçay, Wood, et al 2009;Godard 1991), wasps , octopuses (Tricarico et al 2011), mantis shrimps (Caldwell 1985), salamanders (Kohn et al 2013), and frogs (Bee and Gerhardt 2002). In contrast, class-level recognition (Mateo 2004;Tibbetts and Dale 2007;Wiley 2013) involves much less investment, requiring only that a conspecific be assigned to a certain group, such as mate, offspring or colony-mate.…”