Paternal care in captive collared lemmings (Dicrostonyx richardsoni) and its effect on development of the offspring CATHY M. SHILTON AND RONALD J. BROOKS Department of Zoology, University of Guelph, Guelph, Ont., Canada NIG 2 WI Received December 8, 1988 SHILTON, C. M., and BROOKS, R. J. 1989. Paternal care in captive collared lemmings (Dicrostonyx richardsoni) and its effect on development of the offspring. Can. J. Zool. 67: 2740 - 2745. We examined parental care in captive collared lemmings (Dicrostonyx richardsoni) to determine how this behavior differed between sexes and to test the hypothesis that presence of the male with the litter from parturition to weaning (17 d) would affect preweaning rates of growth, behavioral development, and body size and aggression at sexual maturity. Also, we tested whether stressing the litter, by removal of the female for 8 hld, would alter the effect of the male on the development of pups. We compared four treatments: pups raised with mother only, pups raised with both parents, stressed pups raised with mother only, and stressed pups raised with both parents. Parental behavior was recorded from parturition to weaning. Preweaning development of pups was measured by rate of weight gain, age of eye opening, and development of thermoregulation and righting ability. Comparisons were made between stressed and unstressed litters raised with or without the sire. At 25 d, pups were weighed again and isolated, and at 60 -75 d, their intrasexual aggressive behavior was measured. Presence of the sire did not alter behavior of the dam, and except for lactation, males and females cared equally for the pups. At weaning, stressed pups weighed less than unstressed pups, but this difference disappeared by 25 d. Presence of the sire had no effect on aggression of male or female offspring at 75 d. We concluded that the paternal care shown in this species is either an artifact of laboratory conditions or that it has effects, such as protection of offspring from infanticide or alleviation of thermal stress, that were not examined in this study. SHILTON, C. M., et BROOKS, R. J. 1989. Paternal care in captive collared lemmings (Dicrostonyx richardsoni) and its effect on development of the offspring. Can. J. Zool. 67 : 2740 - 2745. Nous avons CtudiC le comportement des parents chez des Lemmings variables (Dicrostonyx richardsoni) en captivitC afin de dCterminer si ce comportement diffkre chez les mhles et les femelles et afin d'Cprouver l'hypothkse selon laquelle la pdsence du m$le, de la parturition au sevrage (17 jours), peut affecter le taux de croissance, le comportement ou la taille avant le sevrage, et I'aggressivitC au moment de la maturitC sexuelle. Nous avons d'autre part enlevC la mkre pour une durCe de 8 hljours afin de dCterminer si ce stress peut modifier l'effet du mhle sur le dCveloppement des petits. Nous avons comparC les effets de quatre types de conditions : Clevage des petits par la mkre seule, Clevage des petits par les deux parents, Clevage des petits en Ctat de stress par la mkre seule, Clevage des petits en Ctat de stress par les deux parents. Le comportement des parents a CtC not6 de la parturition au sevrage. Le taux de gain de masse, l'hge au moment de l'ouverture des yeux et le dCveloppement de la thermor6gulation et de la capacitC de redressement ont semi de mesures du dCveloppment avant le sevrage. Les portCes stressCes et les portCes normales ont CtC comparCes en prCsence ou en l'absence du pkre. A 25 jours, les petits ont CtC pesCs de nouveau et isolCs et, B 60-75 jours, leur agressivitC intrasexuelle a CtC mesurCe. La prCsence du pkre n'affecte pas le comportement de la mkre et, sauf au moment de l'allaitement, les deux parents sont Cgalement impliquCs dans les soins aux petits. Au moment du sevrage, la masse des petits stressCs Ctait infkrieure B celle des petits normaux, mais la diffkrence Ctait disparue B l'hge de 25 jours. La presence du pkre n'affectait en rien le comportement agressif des petits, mhles ou femelles, 21 l'hge de 75 jours. I1 faut conclure que les soins paternels chez cette espkce sont un artCfact crCC par des conditions de laboratoire ou qu'ils ont des effets qui n'ont pas fait l'objet de cette Ctude, tels la protection des petits contre l'infanticide ou la diminution du stress thermique. [Traduit par la revue] Introduction Paternal care has been observed in several rodents including Peromyscus spp. (Dudley 1974; Hartung and Dewsbury 1979; Xia and Millar 1988), the Mongolian gerbil (Meriones ungui- culatus) (Elwood 1975), the house mouse (Mus musculus) (Priestnall and Young 1978; Barnett and Dickson 1985), and several species of Microtus (Hartung and Dewsbury 1979; McGuire and Novak 1984; Gruder-Adams and Getz 1985; Storey and Snow 1987). Wuensch (1985) lists several reasons for conducting research in paternal care, including the explana- tion of its occurrence and extent. Presumably, the evolution of paternal care involves a trade-off between improved survival of a litter and reduced opportunities for promiscuous mating (Werren et al. 1980; Dewsbury 1985), so we would expect the degree of paternal care to be greatest in monogamous situa- tions and least in promiscuous mating systems. Some compari- sons of paternal care between prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) (Gruder-Adams and Getz 1985; Oliveras and Novak 1986) have supported this hypothesis, whereas others have not (Har- tung and Dewsbury 1979). Paternal care may include direct investments in the off- spring, such as grooming and retrieving pups or huddling with the pups to aid in their thermoregulation (Elwood 1975; McGuire and Novak 1984), or indirect investments, such as nest building or protecting the offspring against predation (Barash 1975) or infanticide (Mallory and Brooks 1978). With paternal care, pups may show increased survivorship (Barnett and Dickson 1985), more rapid physiological development (Dudley 1974; Storey and Snow 1987), a greater degree of early activity such as climbing and rearing (Elwood and Broom 1978), and enhanced aggressiveness as adults (Mugford and Nowell 1972; Wuensch and Cooper 1981). The purpose of this study was to investigate paternal behav- ior in the collared lemming (Dicrostonyx richardsoni) and to measure its effects on the pups. Dicrostonyx richardsoni occu- pies the arctic tundra west of Hudson Bay and displays an interesting suite of reproductive characteristics such as large Printed in Canada 1 Imprime au Canada Can. J. Zool. Downloaded from www.nrcresearchpress.com by 199.201.121.12 on 06/03/13 For personal use only.