Sexual Segregation in White-Tailed Deer: Intersexual Divergence in Digestive Function, Morphology, and Behavior

I monitored patterns of group membership for white-tailed deer (Odocoileus virginianus), in Lincoln County, Minnesota, USA, to evaluate current techniques used to categorize animals when studying sexual segregation. I observed deer by driving a fixed transect approximately 3 times/week in the evening from late April until mid-July 2004. Observations were pooled by week to investigate patterns in group membership associated with date of parturition (late-May). Group membership was defined according to Hirth (1977). In addition, I grouped individuals using a solitary categorization method. Group categorization methods were evaluated based on documented changes in reproductive behavior and physiology related to parturition, and differences in species social structure and reproductive behavior. I hypothesized that the definition for group membership will influence patterns observed in group associations related to temporal changes in reproductive physiology and behavior. Mean (±SE) group size was 1.76 ± 0.05 (n = 746, range 1-11) with a sex ratio (M:F) of 1:2.64 ± 0.01. Hirth’s (1977) method resulted in only slight changes in group composition throughout the sampling period. Timing of physiological and behavioral changes associated with nutrient acquisition and securing of resources and space exhibited by reproductive females with the onset of lactation was accurately reflected by the solitary categorization. With this method, a significant increase in solitary females, a decline in mixed-sexed groups, and slight increases in solitary and male groups occurred near time of parturition. The solitary categorization was sensitive to changes in behavior and physiology exhibited by reproductively active females and their association with males and other females during sexual segregation in summer. I provided examples of differing reproductive strategies, productivity, and social structure between regions and species, and stressed the importance of considering group membership when investigating patterns of sexual segregation in white-tailed deer and other sexually dimorphic ruminants. I monitored digestive function of 3 treatment groups (i.e., male, nonreproductive female and reproductive female) of captive adult (! 2 yrs) white-tailed deer of varying age and reproductive status during 3 consecutive years. Digestive function was monitored by measuring forage and fluid intake rates, body mass, forage and fluid retention rates, and size of incisor arcades. I also monitored patterns of spatial segregation, group membership, and habitat selection of free-ranging white-tailed deer in Lincoln County, Minnesota USA. There was clear divergence in digestive function between reproductively active females and nonreproductive females, and males. After loss of body mass associated with parturition, reproductive females were capable of maintaining body mass throughout lactation, whereas, males and nonreproductive females increased in body mass each year. Reproductive females had higher forage and fluid intake rates during lactation. Intake rates peaked approximately 4 weeks following parturition; water intake also was influenced by ambient temperature. Forage and fluid intake rates of reproductive females remained high during the remainder of the lactation period. Males and nonreproductive females exhibited little variation in forage or fluid intake, and were not influenced by ambient temperature. Diet quality, forage and fluid retention rates, and digestive efficiency did not differ between treatment groups, despite a dramatic increase in intake rates of reproductive females. Incisor arcade of males and females did not differ between sexes. Nonetheless, incisor arcade relative to body mass was greater for females. A larger incisor arcade relative to body mass in females may aid in increasing intake rates beyond that of males and in more efficient digestion and absorption by increasing communition rates of larger quantities of food.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - University Access Only

Discipline thesis:degree_discipline

Wildlife and Fisheries Science

Year

2006

Author dc:creator

• Monteith, Kevin Lee

Contributors dc:contributor

• Jonathan Jenks

• Natural Resources and Conservation

Statement dc:rights

• Copyright © 2006 Kevin Lee Monteith. All rights reserved.

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/549

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-1549