Student Research Projects 2003
Behavioral ecology of plains bison (Bison bison) in Nebraska
Brent Hall, Mount Liberty, OH
Eric Schaad, Bakersfield, CA
Our summer research team spent 11 weeks (June-August) at the Fort Niobrara National Wildlife Refuge, located on the Niobrara River in the Sandhills of north-central Nebraska. In cooperation with the refuge, we conducted a pilot study to assess the feasibility of a multi-year study of the reproductive biology and behavioral endocrinology of their unique herd of bison. The bison herd represents the remnant of the historic herds that once roamed the middle Great Plains, and it is the only public herd in which every animal is individually branded – making it ideal for behavioral research. Our primary mission was to document the reproductive success of bulls during the rut (15 July - August) by directly observing or inferring copulations. This involved dawn-to-dusk monitoring of all tending pairs of bulls and cows in the herd, which numbered up to 40 pairs during peak rut. Using 4WD vehicles for our safety and for rapid maneuvering within the herd, we looked for behavior indicative of receptive cows ready to mate (cow mounting bull, cow tolerating mount attempts) or cows recently copulated (tail up position) so as to observe copulations, or infer copulation when the same bull tended before and after tail-up, respectively. We estimate that 50% of mature bulls (6 years or older) mated at least once during the rut, with the most successful bull recorded to breed 9 cows. Observations were also made during the rut on focal tending pairs to record bull displays (pawing, rubbing, wallowing, bellowing, mounting), aggression (charges and fights), and olfactory investigation of cows (flehmen or lip curl).
Prior to the rut, we observed activity budgets of bull and mixed groups to complete a prior study on bison sexual segregation. We also initiated the very first study on the behavioral endocrinology of bison bulls, using fecal steroid analysis. Fecal samples were collected to compare testosterone levels of bulls during pre-rut, peak rut, and post-rut, and to compare testosterone and stress hormone (cortisol) of dominant and subordinate bulls during the rut. Samples were later processed at the CRES Endocrinology Lab (see below). At the request of the refuge, our team was involved in conducting applied research to assist refuge management. This included documenting space use patterns of the bison herd in the grazing units, a survey of breeding birds in the grassland habitat of the refuge, and an observational study of black-tailed prairie dogs (Cynomys lodovicianus) to estimate the population size. For relaxation, we went to the scenic Niobrara River for picnics, wading, canoeing, birdwatching, and skipping stones. We gathered every week for journal discussions, bible studies, and community meals, and even mounted a camping trip to the Black Hills of South Dakota. The refuge assisted by providing free housing and 4WD vehicles for our team, and were extremely cooperative. By the end of the summer, we had established an excellent relationship with the refuge personnel, and are looking forward to several more years of fruitful research at this outstanding study site. God is good!
Behavioral endocrinology of bison (Bison bison) bulls
Brent Hall, Mount Liberty, OH
Shavonne Fortin, Imperial, CA
Jacquelynn Jella, Santa Rosa, CA
Almost nothing is currently known of the behavioral endocrinology of adult male bison, although the influence of androgens is known to be the key proximate factor underlying male reproductive behavior, aggression, and subsequent mating success in mammals. Upon the completion of summer fieldwork at Fort Niobrara National Wildlife Refuge (see above), our fall semester research team initiated the laboratory component of a project designed to clarify the behavioral endocrinology of bison males. The objective was to compare testosterone levels of bulls during pre-rut (June), peak rut (15 July-15 August), and post-rut (September), and to compare levels of testosterone and stress hormone (cortisol) in dominant and subordinate bulls during the rut. Because gonadal steroid hormones and their metabolites in feces accurately reflect endocrine activity, fecal steroid techniques have recently emerged as a non-invasive and convenient means of determining the reproductive status of free-ranging wildlife. In the field, fecal samples were collected from known bulls when defecation was observed, placed in plastic vials, and subsequently stored at -20o C until shipped overnight on dry ice to San Diego. Samples were later processed at the CRES (Center for the Reproduction of Endangered Species) Division of Endocrinology lab at the San Diego Zoo under the supervision of collaborators Dr. Valentine Lance and Dr. Lynn Patton. Frozen fecal samples were freeze-dried in a lyophilizer and subsequently ground by hand with mortar and pestle. Testosterone and cortisol were then extracted from 0.2 g of each sample with ethyl ether, and assayed using radioimmunoassay. Although the endocrinology of the female reproductive cycle has been previously investigated, this is the first study to explore the endocrinology of free-ranging bison bulls. With preliminary results looking very good and a working relationship established, we are excited about future collaborative work with the Endocrinology lab.
Student Research Projects 2004
Reproductive biology of bison (Bison bison): behavior, genetics, and conservation
Nikki Beckley, Merced, CA
Desiree Boyle, La Mirada, CA
Michael Dillenbeck, Quartz Hill, CA
Matt Herrick, Fresno, CA
Our summer research team spent 11 weeks (June-August) at the Fort Niobrara National Wildlife Refuge (FTN), located on the Niobrara River in the Sandhills of north-central Nebraska. Working with the US Fish & Wildlife Service (USFWS), we completed the 2nd year of a multi-year study on the reproductive biology of the FTN bison herd. This herd represents the remnant of the historic herds that once roamed the middle Great Plains, and it is the only public herd in which every animal is individually branded – making it ideal for behavioral research. Our primary mission was to document the reproductive success of bulls during the rut by dawn-to-dusk monitoring of all breeding (tending) pairs of bulls and cows in the herd. This year, we initiated a complementary genetic study that will involve parentage analysis of all 2004 calves in order to independently determine mothers and sires using blood and skin tissue samples. The genetic parentage tests will be done in collaboration with Texas A&M University. In combination with the behavioral observations, we will be able to examine some long-held assumptions about bison reproduction, gain new insights into their breeding biology, and test the reliability of behavioral data for determining parentage. The summer research team continued to study the behavioral endocrinology of bison using fecal steroid analysis. Fecal samples were collected to (1) assay the level of glucocorticoid (cortisol, a stress hormone) of high- and low-ranking bulls, and (2) determine the estrus dates of cows by measuring progesterone. Fecal samples will be processed in collaboration with the CRES Endocrinology Lab of the Zoological Society of San Diego. In collaboration with UC Davis, our team also initiated a collaborative study of bison acoustical communication. The goal is to determine the function and acoustical structure of the “bellow” vocalization. We recorded the bellows of breeding bulls and conducted playback trials to establish a protocol for next season. At the request of the refuge, our team also conducted applied research to assist refuge management. This included a census of the prairie dog town, a trapping survey of the American burying beetle, and identification of suitable habitat for an endangered plant. For relaxation, we went to the scenic Niobrara River for picnics, wading, and canoeing, and several of the students enjoyed water sports at a nearby lake and paintball games with refuge friends. We gathered every week for Bible study and sharing, for discussions of journal articles, and for community meals. The refuge continued to assist us by providing housing and 4WD vehicles, and we are grateful for their support.
Behavioral endocrinology of bison (Bison bison) bulls and cows
Michael Dillenbeck, Quartz Hill, CA
Kevin Yarbrough, Phoenix, AZ
Following up on the publication of our results from last year’s study of bull androgrens in the journal Hormones & Behavior, Michael and Kevin are working hard this semester with Dr. Lynn Patton of the CRES Endocrinology lab to extend that work into new areas. CRES (Center for the Reproduction of Endangered Species) is the research arm of the Zoological Society of San Diego, and has one of the nation’s top wildlife endocrinology labs. This year, we are focusing on (1) determining the level of glucocorticoids (cortisol) in bison bulls to compare stress in high- versus low-ranking individuals, and (2) measuring the level of progesterone in cows in order to pinpoint estrus dates in tended and non-tended cows. Because steroid hormones and their metabolites in feces accurately reflect endocrine activity, fecal steroid techniques have recently emerged as a non-invasive and convenient means of determining the endocrinology of free-ranging wildlife. From June-September, we opportunistically collected fecal samples of bulls and cows. Samples were frozen and shipped to CRES on dry ice at the end of the summer. Frozen fecal samples were freeze-dried in a lyophilizer and subsequently ground and sifed by hand with mortar and pestle in the lab. Cortisol and progesterone will later be extracted from each sample and assayed using radioimmunoassay. The results will then be compared with our observational data to see how well cortisol correlates with rank, and how well progesterone matched up with tending status.
Sabbatical Research Activities
This year the Lord has opened up many doors of opportunities for collaborative ventures that will expand the scope and importance of the bison study. During July and August, we initiated a collaborative study of bison acoustical communication. I worked daily with UC Davis students Megan Wyman (Ph.D. student) and Margaret Swisher (undergraduate) to record the bellow vocalization of breeding bulls. These acoustical archives will be analyzed at UCD using sophisticated acoustical software. Collaborators Drs. Lynette and Ben Hart from UCD visited in early August to confer and brainstorm. After all the undergraduates left in mid-August, I continued to work with Megan Wyman to construct a 2-dimensional visual model of a bellowing bull and conduct playback trials to establish a protocol for next season. In conjunction with the acoustical project, I also collected a bison head during the roundup and delivered it to the Omaha Zoo, where Dr. Ed Walsh and other collaborators will examine the anatomy and neurophysiology of the bison vocal apparatus. In November and December I travel to UC Davis to confer with my collaborators on this project.
In cooperation with USFWS personnel at the refuge, we initiated a genetic parentage study that will greatly enhance the accuracy and value of our behavioral observations. During the month of September, I worked with my wife, Emma Mooring, to mark and biopsy dart as many calves as possible for skin tissue collection. When a calf was observed nursing (indicating the cow was the mother), I shot a paint dart to produce a unique mark, then shot a biopsy dart to collect a skin core sample. These samples were frozen, and will be used to validate the maternal assignments from the parentage analysis. We collected 101 biopsy samples out of 113 calves. I participated in the herd roundup at end of September, at which time every calf was run through the chute, ear-tagged and blood taken for blood cards. Because of the paint dart markings, we were able to associate many of the ear-tagged calves with their mothers. These samples are now being stored by USFWS prior to laboratory analysis. I have met and arranged collaboration with Dr. Jim Derr of Texas A&M, whose lab will conduct the blind cross-matching analysis using samples from all adults and calves in the herd. I also am collaborating with Dr. Cecilia Penedo of Veterinary Genetics Lab at UC Davis to do the independent validation work. I am very excited about this new study, and am convinced that, if the necessary funds can be raised, this project can provide major new insights into bison reproductive biology.
In October, my family and I moved out of our trailer on the refuge into a rental house in the town of Valentine, where our children are going to school for the year. At present, I am continuing to work with the bison herd in their winter range north of the Niobrara River, where the herd is driven after roundup. By being in the field 1-2 days per week, I will (1) collect fecal samples to establish the annual cycle of hormones (androgens, cortisol, progesterone), and (2) monitor late season breeding activity. These observations have already born fruit, as it is clear that a significant amount of breeding occurs very late in the season. In April, when the herd is driven south of the Niobrara River into the summer units, I will resume daily observations in order to record births, observe maternal interactions, and document dominance among bulls. In June, my family and I will move back into our housing on the refuge, in preparation for a new batch of summer research students. Throughout the fall, winter, and spring, I will work on manuscripts, write grant proposals, and meet with colleagues. I will travel to UC Davis to meet with collaborators during November-December and begin writing an NSF-RUI grant proposal to fund this project for the next 3 years. I will also be writing a grant proposal for the National Bison Foundation and any other funding opportunities that come up.
Fitness consequences of sexually selected acoustical signaling in American bison
NSF Lay Summary
It is now clear that sexual selection (selection for traits that increase mating success) has led to the evolution of sexually dimorphic attributes in males. Whether in the context of male-male contests or female mate choice, many of these traits act as signals that contain information about mate quality. Studies of invertebrates and small vertebrates have revealed that such signals are often assessed by receivers so as to choose tactics that maximize fitness (e.g., reproductive success). We know very little about how signal assessment works in large mammals, in which multiple and changing signals must be evaluated concurrently over the course of the breeding season. The goal of this research is to investigate the production and assessment of the bellow vocalization of male bison, which is the most conspicuous hallmark of the bison breeding season. The aim is to clarify the role of the bellow signal in the reproductive success of breeding males. Our central hypothesis is that there is useful information contained in bellows that other bison can evaluate and use to their advantage. We have formulated this hypothesis based on strong preliminary findings that indicate that a number of bellow acoustical features reflect the quality of the signaling male. A necessary prerequisite to this study is an understanding of how reproductive success relates to mating performance and attributes that other bison may use to assess male quality. Therefore, an integral component of this project will be the use of molecular techniques to determine genetic parentage for comparison with male mating behavior.
To test our hypothesis, we will study the bison population at Fort Niobrara National Wildlife Refuge, in which all adults are individually marked and open grassland terrain enables constant surveillance of breeding behavior. We will utilize the expertise of a multidisciplinary team of 5 collaborators to perform the laboratory analyses for genetic parentage, acoustics, and behavioral endocrinology that will complement behavioral observations. Dawn-to-dusk observations will document breeding behavior, and genetic parentage analyses will assign maternity and paternity to all calves. Bellowing will be recorded from dominant and subordinate males, and recordings analyzed to compare acoustical features with measures of signaler quality (reproductive success, competitive ability, condition, physiological state) and motivation (estrous stage of tended female, number of challenging males). Playback experiments will be conducted at night to evaluate the response of males to the acoustical features of synthesized bellows. Fecal samples will be used to measure male sex and stress hormones (associated with dominance and aggression), and female sex hormones (to determine hormonal estrus). Our results will provide insights into similar species in which vocalizations play a role in breeding. Field and lab participation by undergraduate and graduate students will offer valuable learning experiences and preparation for future careers in science. Finally, information obtained on bison reproductive biology can be applied to the conservation of this keystone species and symbol of the American West.