Grouping increases the ability of the social rodent, Octodon degus, to detect predators when using exposed microhabitats

Abstract

We examined the hypothesis that a main benefit of group‐living in the hystricognath rodent, Octodon degus (common degu), is to decrease individual risk of predation. During a first series of field observations, we contrasted group size of degus when using covered microhabitats with that of degus using exposed patches. During a second set of field observations, we assessed how distance to detection and to escape by degus varied with group size upon the approach of a potential human predator. Degus in exposed patches formed larger groups than degus in covered microhabitats. After excluding the influence of nearest burrow to focal subjects, we found that degus of larger groups detected an approaching human predator at a greater distance than degus of smaller groups. Likewise, degus of larger groups escaped to nearby burrows at a greater distance from the approaching predator than degus of smaller groups. All these pieces of evidence support the predatory risk hypothesis according to which group‐living in degus functions to reduce the risk of predation.

Comparing composition of social groups, mating system and social behaviour in two populations of Microcavia australis

“…located at higher altitude, in a more rigorous environment, exhibit a larger group size with more tolerance between individuals, and the greater number of marmots per group would reduce the loss of heat (Barash 1973(Barash , 1974Arnold 1988Arnold , 1990. Females of Octodon degus share a communal nest, which, among other things, allow them to improve thermoregulation (Ebensperger and Wallen 2002;Ebensperger et al 2004) because loss of body warmth is reduced by their crowding together in groups, and which becomes more efficient the larger the group size (Arnold 1988). The degree of behavioural specialization among individuals appears to increase with group size (Lacey 2000) and the total time and energy that animals allocate to specific activities, e.g.…”

Behavioural and morphological strategies by small savannah rodents to avoid predation

“…Ebensperger and Wallem (2002) showed that group-living in Octodon degus (hystricognath) decreased individual risk of predation to human subject. Group-living in C. bishop as an anti-predator strategy should also be further investigated.…”

“…On the other hand, the opportunistic consumption or "avoidance" of this Echymyidae by the burrowing and barn owls, respectively, may be not only related to hearing capability, but also to differences in predator (145 g and 480 g, respectively) and prey (208.7 ± 65.2 g) sizes and difficulties in handling such large prey (Bueno and Motta-Junior 2008). As C. bishopi has a predominant quadrupedal locomotion, here considered the least efficient locomotion against predator attacks, it has to rely on other anti-predator strategies, such as hopping, tail loss (AAB, personal observation), digging, living underground (Ávila-Pires and Wutke 1981; Vieira 1997) and group-living (Ebensperger and Wallem 2002). Hopping, digging, jumping and ground activities are strategies used by other Echimyidae species (Manaf and Oliveira 2000) and by subterranean tuco-tucos (Ctenomys sp.)…”

“…In the case of small rodents, inflated bullae (Webster 1962;Kotler et al 1988), bipedal locomotion with high running speeds and erratic escapes (zigzagging) (Bartholomew and Cary 1954;Djawdan and Garland 1988;Kotler et al 1988;Corley et al 1995;Taraborelli et al 2003;Tabeni et al 2012), intermittent locomotion (McAdam and Kramer 1998;Kramer and McLaughlin 2001;Vásquez et al 2002;Taraborelli et al 2011), lower activity on full moon nights (Clarke 1983;Simonetti 1989;Daly et al 1992;Hughes and Ward 1993;Hughes et al 1994;Vásquez 1994;Orrock et al 2004;Upham and Hafner 2013), use of bushy microhabitats (Price et al 1984;Kotler et al 1988;Pusenius and Ostfeld 2002;Orrock et al 2004;Bisceglia et al 2011;Tabeni et al 2012 and Caswell 1951) and group-living (Yáber and Herrera 1994;Ebensperger and Wallem 2002) are all described as efficient antipredator strategies.…”

Effects of group size on nest attendance in the communally breeding colonial tuco-tuco

“…The selective factors favoring communal nesting may act directly upon the adults that share a nest (e.g., increased predator detection; Macdonald 1981;Pilastro 1992;Ebensperger and Wallen 2002) or they may act upon the young reared in communal nests (e.g., increased protection from infanticide; Brown and Burt 2004;Manning et al 1995;Ebensperger 1998), thereby enhancing the fitness of parents that nest together. Because different selective factors may have distinct or even competing effects on the actions of individuals, it is important to understand how the various potential benefits of communal nesting interact to shape the behavior of animals that live and rear their young together.…”