Ontogeny of agonistic behaviour in dispersing blind mole rats (spalax ehrenbergi)

Abstract

The blind mole rat (Spalax ehrenbergi) is a solitary and aggressive fossorial rodent that inhabits its own individual tunnel system. Mole rats breed mainly in the winter, giving birth to a litter of three to four young on average [Nevo (1961) Mammalia 25:127–143]. Intraspecific interactions between adults occur mostly during the winter, which is the rainy season in Israel; after parturition, interactions occur between the mother and her offspring and between the siblings themselves until dispersal. Until now, the subterranean habitat of mole rats has prevented direct observation in the wild. Thus, there has been no direct evidence for the proximal factors that drive juvenile mole rats out of the maternal tunnel system as they shift from the social life‐style of the young to the solitary life‐style of the adult. In the present study, female mole rats were caught in the wild with their offspring and brought to the laboratory. The dispersal process of the young from the maternal nest was followed under two housing conditions: (1) restricted housing, simulating the physical conditions under which dispersal is delayed past the usual age, as often occurs during late winter floods in the field in areas of nonporous clay soils, and (2) nonrestricted housing, simulating the physical conditions that allow the young to disperse from their maternal tunnels at any time. In each housing condition, the mothers raised either one or three pups. During pup development, we monitored both maternal and juvenile agonistic variables during intraspecific interactions. Five major behavioural phases were identified during the ontogeny of the mole rat pups. Maternal aggression toward pups increased mainly in the first three phases of pup development, and sibling aggression increased from the third phase until dispersal. Under the restricted housing conditions, there was a delay in both the appearance of aggression in the “family group” as well as in dispersal age compared with the nonrestricted conditions. In the nonrestricted conditions, increased litter size resulted in delay in dispersal age. We suggest that the main proximate factor initiating natal dispersal is increased intolerance and aggression among siblings rather than maternal aggression. Only after the young began dispersing from the maternal tunnels did maternal aggression dramatically increase, thus preventing the offspring from returning. However, following floods, inhibition of aggression may enable the mole rat pups to stay with the family group and to disperse later when the physical conditions permit it. Aggr. Behav. 24:455–470, 1998. © 1998 Wiley‐Liss, Inc.

The social network: Neural control of sex differences in reproductive behaviors, motivation, and response to social isolation

“…Interestingly, within these diverse social lifestyles, an additional layer of diversity exists with respect to sexual dimorphism in parental care and aggression [ 220 ]. Presented from top to bottom—eusocial rodents: naked mole-rat [ 219 , 221 , 222 ], Damaraland mole-rat (picture courtesy of Dr. Markus Zöttl) [ 223 , 224 , 225 ]; social group/monogamous living: house mouse [ 33 , 59 , 219 ], prairie vole (picture courtesy of Prof. Larry Young) [ 219 , 226 , 227 ]; facultatively solitary: Syrian hamster [ 228 , 229 ], meadow vole [ 219 , 226 ]; and solitary: blind mole-rat [ 197 , 199 , 203 , 230 ], Patagonian tuco-tuco (picture courtesy of Prof. Annaliese Beery) [ 231 , 232 ]. The symbols ♀ (female) and ♂ (male) denote sexual dimorphism or sex similarities for each behavior within a given species.…”

“…Interestingly, even within some families of subterranean rodents, social strategies range from solitary to eusocial [ 42 , 193 , 195 ], providing a unique opportunity to perform comparative studies and investigate the neural and evolutionary substrates driving the transitions across the ‘social scale’ (see Figure 1 ). Among these subterranean rodents, the blind mole-rat (BMR, Spalax ehrenbergi ) exhibits one of the most solitary and aggressive life strategies, with relatively low levels of behavioral sex differences [ 196 , 197 , 198 , 199 , 200 , 201 ] (see Figure 1 ). Each individual excavates its own tunnel system to fit its body width and never leaves it unless forced to do so [ 196 , 201 ].…”

“…During the rainy breeding season, it appears that the males socially communicate with potential females from a long distance and orient themselves to the female territory [ 204 , 205 ]. The males resume their solitary lifestyle immediately after successful copulation, while the females care for the pups alone [ 197 , 199 , 201 , 204 ]. Therefore, in order to ensure survival and reproductive success, BMRs must constantly be aware of the location and social status (e.g.…”

Pup Shoving by Adult Naked Mole‐Rats

“…(2) Natal dispersal: Maternal aggression frequently is a prelude to dispersal from the natal home range or territory, for example in pikas ( Ochotona princeps : Smith 1974; Whitworth 1984), golden hamsters ( Mesocricetus auratus : Rowell 1961; Schoenfeld and Leonard 1985), woodchucks ( Marmota monax : Barash 1974), and Mediterranean blind mole‐rats ( Spalax ehrenbergi : Zuri and Terkel 1998). Such aggression is a manifestation of an evolutionary conflict between females and their offspring over how long young should remain near home when their presence reduces the mother's ability to rear future offspring.…”

Steppe rodents at the edge of their range: A case study of Spalax microphthalmus in the north of Ukraine

“…Estimation of settlement density. The species' abundance can be estimated if we accept that one series of molehills belongs to a single individual and that mole rats are solitary animals (Zuri & Terkel, 1998;Korobchenko et al, 2010). Respectively, we can estimate the number of individuals on a hectare by the number of molehill groups.…”