Sexual Dimorphism in Size, Relative Size of Testes, and Mating Systems in North American Voles

Heske, Edward J.; Ostfeld, Richard S.

doi:10.2307/1381789

Cited by 156 publications

(146 citation statements)

References 42 publications

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“…This distribution sets the stage for monopolization by males; if the aggregation of females is defensible, there exists a high potential for polygyny (Emlen and Oring, 1977). In polygynous species, males typically defend territories during the breeding season that contain home ranges of one to several females (Heske and Ostfeld, 1990). Females may, or may not, show territorial behavior.…”

Section: Introductionmentioning

confidence: 99%

Social Organization of Neotoma micropus, the Southern Plains Woodrat

Conditt¹,

Ribble²

1997

American Midland Naturalist

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ABSTRACT.-This study described the social organization of Neotoma micropus, the southern plains woodrat, using radiotelemetry. We studied woodrats from September 1994 through April 1995 at the Urban Wilderness Reserve in S Bexar County, Texas. Sixteen individuals (three adult males, 11 adult females, and two subadult males) were radiocollared and located in the evening or early morning duringJanuary and February. Seventy-four percent of female radiolocations and 57% of male radiolocations were from their respective nests. No more than one adult individual was observed at any nest at the same time. Males had significantly larger (x = 1899 m2) home ranges than females (x = 220 m2). Male home ranges overlapped female home ranges more (35.9%) than female ranges overlapped other female home ranges (11.9%). Survival rates were similar for males and females. The results confirm previous studies indicating that these woodrats are asocial. The spacing of male and female home ranges indicated that these woodrats probably have a promiscuous mating system.

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Section: Introductionmentioning

confidence: 99%

Social Organization of Neotoma micropus, the Southern Plains Woodrat

Conditt¹,

Ribble²

1997

American Midland Naturalist

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“…Such differences in testis size are thought to be due to greater intermale sperm competition and/or higher copulatory frequencies in males in the multimale breeding groups. Moller (1988,1989) (Heske & Ostfeld, 1990;Pierce et ai, 1990) although there is some evidence that individuals of this species may sometimes, especially in winter, form complex breeding units (Getz et ai, 1987 (Breed, 1982(Breed, , 1986, which is about an order of magnitude smaller than the mean testis mass of mammals of comparable body size (Kenagy & Trombulak, 1986). These species also have small epididymides and low epididymal sperm stores (Breed, 1982(Breed, , 1986Peirce & Breed, 1989) and studies on sperm morphology of one of these species, N. alexis, have shown a high degree of pleiomorphism of acrosome, nucleus and overall sperm head shape (Breed & Sarafis, 1983;Suttie et ai, 1988).…”

Section: Discussionmentioning

confidence: 99%

Mating behaviour and insemination in the hopping mouse (Notomys alexis)

Breed

Washington²

1991

Reproduction

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Summary. Hopping mice have extremely small testes and a reduced complement of male accessory sex glands. Nevertheless, >1000 spermatozoa populate the isthmus of the oviduct after each insemination and a range of morphological types is found similar to that in the male tract. When females are primed with gonadotrophins they sometimes lock with more than one of the males within the group and in the present study two inseminations sometimes took place at the one oestrus. There is thus the possibility for intermale sperm competition within the female tract of these animals.

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“…and the red vole (Myodes rutilus Pall.). For all species, there is evidence for a multi-male mating system [25][26][27][28][29].…”

Section: Materials and Methods (A) Study Site And Capture Methodsmentioning

confidence: 99%

Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

Klemme

Soulsbury

Henttonen³

2014

Proc. R. Soc. B.

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Across species, there is usually a positive relationship between sperm competition level and male reproductive effort on ejaculates, typically measured using relative testes size (RTS). Within populations, demographic and ecological processes may drastically alter the level of sperm competition and thus, potentially affect the evolution of testes size. Here, we use longitudinal records (across 38 years) from wild sympatric Fennoscandian populations of five species of voles to investigate whether RTS responds to natural fluctuations in population density, i.e. variation in sperm competition risk. We show that for some species RTS increases with density. However, our results also show that this relationship can be reversed in populations with large-scale between-year differences in density. Multiple mechanisms are suggested to explain the negative RTS-density relationship, including testes size response to density-dependent species interactions, an evolutionary response to sperm competition levels that is lagged when density fluctuations are over a certain threshold, or differing investment in pre-and post-copulatory competition at different densities. The results emphasize that our understanding of sperm competition in fluctuating environments is still very limited.

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Sexual Dimorphism in Size, Relative Size of Testes, and Mating Systems in North American Voles

Cited by 156 publications

References 42 publications

Social Organization of Neotoma micropus, the Southern Plains Woodrat

Social Organization of Neotoma micropus, the Southern Plains Woodrat

Mating behaviour and insemination in the hopping mouse (Notomys alexis)

Contrasting effects of large density changes on relative testes size in fluctuating populations of sympatric vole species

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