Abstract
Immature mammals require opportunities to develop skills that will affect their competitive abilities and reproductive success as adults. One way these benefits may be achieved is through play behavior. While skills in developing use of tusks, antlers, and other weapons mammals have been linked to play, play in venomous animals has rarely been studied. Javan slow lorises (Nycticebus javanicus) use venom to aid in intraspecific competition, yet whether individuals use any behavioral mechanisms to develop the ability to use venom remains unclear. From April 2012 to December 2020, we recorded 663 play events and studied the factors influencing the frequency of play and the postures used during play in wild Javan slow lorises. Regardless of the presence of siblings, two thirds of play partners of young slow lorises were older and more experienced adults. Young lorises engaged in riskier behaviors during play, including using more strenuous postures and playing more in riskier conditions with increased rain and moonlight. We found that play patterns in immature lorises bear resemblance to venom postures used by adults. We suggest that play functions to train immature lorises to deal with future unexpected events, such as random attacks, as seen in other mammalian taxa with weapons. Given the importance of venom use for highly territorial slow lorises throughout their adult lives and the similarities between venom and play postures, we cannot rule out the possibility that play also prepares animals for future venomous fights. We provide here a baseline for the further exploration of the development of this unique behavior in one of the few venomous mammals.
Highlights
Different types of weapons, such as antlers, tusks, horns, canines, and toxins have evolved in numerous animal taxa [1,2] In many of these species, weapons are used to defend vital resources that directly or indirectly translate into mating opportunities [2]
One way to study the development of adult behaviors is through play, as it is hypothesized that play may be one way in which young individuals learn and practice behaviors that will be useful as adults [7,8]
When considering overall age of play partners, we found that immature slow lorises played more often with their parents than with other siblings
Summary
Different types of weapons, such as antlers, tusks, horns, canines, and toxins have evolved in numerous animal taxa [1,2] In many of these species, weapons are used to defend vital resources that directly or indirectly translate into mating opportunities [2]. In species that possess such weapons, sexually dimorphic male and female adults assume distinctly different roles. The evaluation of adult behavior requires a clear understanding of ontogeny [4,5,6]. The causation and function of species-specific behavior patterns are better understood through the comparative study of behavioral development [5]. One way to study the development of adult behaviors is through play, as it is hypothesized that play may be one way in which young individuals learn and practice behaviors that will be useful as adults [7,8]
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