Hip Glands in a Natural Population of Montane Voles (Microtus Montanus)

Great Basin Naturalist

Volume 44 Number 3 Article 11

7-31-1984

Hip glands in a natural population of montane voles (Microtus montanus)

Craig R. Groves Idaho State University, Pocatello

Barry L. Keller Idaho State University, Pocatello

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Recommended Citation Groves, Craig R. and Keller, Barry L. (1984) "Hip glands in a natural population of montane voles (Microtus montanus)," Great Basin Naturalist: Vol. 44 : No. 3 , Article 11. Available at: https://scholarsarchive.byu.edu/gbn/vol44/iss3/11

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. HIP GLANDS IN A NATURAL POPULATION OF MONTANE VOLES {MICROTUS MONTANUS)

Craig R. Groves^'^ and Barry L. Keller'

Abstract.— We recorded the occurrence of hip glands in a population of montane voles {Microttis montanus) in southeastern Idaho. Sexual maturity was positively associated with the presence of hip glands in both males and females. Significantly more males than females pos.sessed hip glands. Males and females with hip glands were significantly heavier than individtials without glands. The possible function of hip glands in scent marking, aggression, and population fluctuations is discussed.

Many species of Microtiis possess hip or 1979. Details on the study area and trapping flank glands. The histology and taxonomic methods are provided in Groves and Keller significance of these sebaceous glands were (1983). reviewed by Quay (1968) and Skurat (1969). Howell (1924) first described hip glands in a Results and Discussion population of montane voles {Microtiis montanus) in California. More recently, Jannett Hip glands occurred on 65% of male M. (1978) and Lyons (1979) reported the pres- montanus (Table 1). There was a positive as- ence of hip glands in populations of M. mon- sociation between sexual maturity in males tanus in Wyoming and Idaho, respectively. and the presence of hip glands (X^ = 25.54, Although these glands have been examined in P < 0.01). Males with hip glands were signif- several laboratory studies (e.g., Jannett 1981), icantly heavier than males without glands {t limited quantitative data are available on the = 7.75, P < 0.01). Compared to males, few- occurrence of these glands in wild popu- er females (12%) possessed hip glands (X^ = lations. During a population study of small 55.60, P < 0.01). Like males, sexual maturity mammals in southeastern Idaho, we recorded in females was positively associated with the the presence or absence of hip glands for 86 presence of hip glands (X^ = 6.23, P < 0.05). male and 99 female M. montanus (Groves Females with hip glands were also heavier and Keller 1983). The purpo.se of this paper than females without glands {t = 2.50, P < is to compare reproductive characteristics 0.01). and weights of voles in which hip glands Howell (1924), Jannett (1978), and Lyons were present or absent. (1979) observed that only a few female M. montanus possessed hip glands in wild popu- well-developed hip Methods lations, whereas most glands occurred in large males. Our data sup- Our research was conducted on the Radio- port their notions that only a few females active Waste Management Complex of the possess hip glands in natural populations. In Idaho National Engineering Laboratory Site. contrast, hip glands occur commonly in both Vegetation in the areas where voles were live sexes in many species of Microtus (Quay trapped consisted primarily of crested wheat- 1968). grass (Agropyron cristatum) that had been Our data suggest that weight (age) and sex- seeded over areas where low-level radio- ual maturity are related to the development active waste was interred. We recorded data of hip glands in M. montanus. Lyons (1979) on the occurrence of hip glands during reported a positive correlation between mean monthly trapping intervals from April to July monthly weights of male M. montanus and

'Department of Biology, Idaho State University. Pocatello, Idaho 83209. 'Present address: The Nature Conservancy, 2118 Grant. Boise, Idaho 8.3706.

468 July 1984 Groves, Keller: Microtus Hip Glands 469 the percent occurrence of hip glands. Jannett 1979). Lyons (1979) conducted laboratory ex- (1978) indicated that hip gland development periments that indicated odors from hip is androgen-dependent in male and female M. glands of male M. montanus may be impor- montanus, as well as several other microtine tant for individual and group recognition. species. Clarke and Frearson (1972) positive- Stoddart et al. (1975) compared flank gland ly associated hip gland development in male secretions for different sexes, age classes, and M. agrestis with sexual maturity. Correlations poulations of Arvicola terrestris. They found between reproduction and hip gland occur- marked differences between age classes and rence were also reported for male and female among populations, suggesting a strong social M. xanthognathus (Wolff and Lidicker 1979), influence on the quality of flank gland secre- male and female M. townsendii (Maclsaac tions. The precise function of the various spe- 1977), and male M. californicus (Lidicker cialized glands (Quay 1962, 1965, 1968) in 1980). In a long-term stvidy of population dy- microtine rodents is uncertain, but it would namics of M. pennsylvaniciis, Tamarin (1981) appear that these glands exude chemicals observed only one vole with hip glands, and (pheromones) that may facilitate recognition this individual was an old, sexually mature among individuals (Richmond and Stehn male. In addition, Boonstra and Youson 1976, Beard 1978, Lyons 1979, Jannett 1981). (1982) reported well-developed hip glands in Additionally, they may integrate breeding of breeding males of M. pennsylvaniciis as re- sexually mature individuals (Keller, in press). vealed by histological examination, although Thus, hip gland marking may be important in no consistent relationship was observed be- territorial defense, individual recognition, tween the degree of hip gland development and other social interactions. and breeding status in females. Our observations of hip gland occurrence Jannett (1981) reported that scent marking in an increasing M. montanus population sug- with hip glands by male M. montanus in the gest that these glands may also be important laboratory is rare, although other species of in behavioral changes that occur in fluctuat- Microtus do exhibit marking behavior with ing vole populations (see review, Krebs and hip or flank glands (e.g., Wolff and Johnson Myers 1974). Jannett (1981) has demonstrated that scent secretions from hip glands of male M. montanus mediate both intra- and inter- Table 1. Reproductive characteristics and mean specific attacks. He hypothesized that devel- weights of montane voles in which hip glands were pres- opment of hip glands at puberty stimulates ent or absent. Males with scrotal testes were considered adult and to be in reproductive condition. Females who had pre- aggressive interactions between viously lactated and/or possessed open pubic symphyses pubertal voles, and may also reduce recruit- or perforate vaginas were considered to be sexually ment of voles into the breeding population. mature. Future research efforts should investigate the role that secretions from hip glands may play Hip glands in different phases of a microtine cycle. Present Absent Males Acknowledgments Number of sexually mature individuals 44 6 This research is a contribution from the Idaho National Engineering Laboratory Eco- Number of individuals not sexually mature 12 24 logical Studies Program, supported by grants from the Office of Health and Environmental Mean weight (g) ± S.E. 41.2 ± 1.3 24.0 ± 2.0 the Nuclear Fuel Cycle and (n) (56) (30) Research and Waste Management Division, U.S. Depart- Females ment of Energy, and Grant 412, Faculty Re-

Number of sexually search Committee, Idaho State University, to mature individuals 12 56 B. L. Keller. Number of individuals not sexually mature 31 Literature Cited

weight S.E. 39.7 ± 2.1 29.6 ± 1.5 Mean (g) ± Beard, H. B. 1978. Hormonal influence on the social be- (n) (12) (87) havior of the vole, Microtus ochrogaster: effects of 470 Great Basin Naturalist Vol. 44, No. 3

photoperiod, temperature, gonadectoiny, pre- 1979. gland occurrence and function in Lyons, T. J. Hip putialectomv and oral angle gland removal. Un- Microtus montanus. Unpublished thesis. Idaho published dissertation. Iowa State Univ., Ames. State Univ., Pocatello. 50 pp.

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