Sierra Nevada Bighorn Sheep Proposal

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Sierra Nevada Bighorn Sheep Proposal Emily Cline Background: The Sierra Nevada bighorn sheep population began being threatened as early as the 1850s with the arrival of gold miners to the Sierra

1 Sierra Nevada Bighorn Sheep Proposal Emily Cline Background: The Sierra Nevada bighorn sheep population began being threatened as early as the 1850s with the arrival of gold miners to the Sierra Nevada region. The miners would kill the sheep for food and later farmers began raising domestic sheep populations near the bighorn territory. The introduction of domesticated sheep exposed the Sierra Nevada bighorns to diseases that they had no resistances to. The population slowly declined since the mid-1800s until 1979 when only two herds of bighorns totaling 125 individuals remained. The Sierra Bighorn Interagency Advisory Group was formed in 1981 to address the low bighorn population. The efforts to increase the bighorn population was somewhat successful, but was hindered by legal constraints. In 1999 the Sierra Nevada Bighorn Sheep Foundation and four other organizations petitioned to put the Sierra Nevada bighorn on the endangered species list; in 2000 the bighorn was listed as a state and federally endangered species. The bighorns have since increased in numbers but only to about 400 individuals. Figure 1. Sierra Nevada bighorn sheep (Ovis canadensis sierra). The ewe to the right has a radio collar on to track herd movements. (Sierra Nevada Bighorn Sheep Foundation) The animals are tracked using radio collar telemety units and in 2010 the California Department of Fish and Game along with Yosemite Park began using GPS collars to track the bighorns movements. It s important to track the animals to ensure they don t come in contact with domestic sheep in nearby grazing grounds and to see what grazing lands the bighorns travel to during different seasons. The Sierra Nevada bighorn sheep would be a good GIS study subject because they are a unique and endangered species that has very constrained environmental 1

2 requirements. The bighorns are worth investing time in conserving because they are expected to make a good recovery as long as predation and disease can be kept to a minimum and because they are an important member in the alpine ecosystem of the Sierra Nevada. With the help of the GPS data being currently collected and with some additional data very comprehensive GIS maps could be made which would help monitor the factors that are currently limiting the bighorn populations such as predation, forage quality and availability, and genetic diversity. Literature Review: Sierra Nevada bighorn sheep (Ovis canadensis sierrae) were particularly susceptible to becoming endangered after their first encounter with humans in part because of their very specific habitat and the required elevation ranges for their survival. Sierra Nevada bighorns inhabit the highest peaks of the Sierra Nevada at an elevation around 13,000 feet to and their lowest range is around 4,700 feet elevation (see Figure 2) (U.S. Fish and Wildlife Service 2007). Figure 2. The inhabited and uninhabited recovery units or distribution ranges of the Sierra Nevada bighorn sheep. Notice how the recovery units are segregated and not one continuous habitat range. (Sierra Nevada Bighorn Sheep Foundation). These restricted elevation ranges keep the bighorns confined and can segregate herd groups. The restricted habitat helps compound the main limiting factors in bighorn population recovery which include: disease (primarily a type of pneumonia), predation (mountain lions), low population 2

3 numbers and limited distribution, availability of open habitat, and potential further loss of genetic diversity as a result of small populations and segregation (U.S. Fish and Wildlife Service 2007). Although the Sierra Nevada bighorns have many limiting factors that can affect population growth, the species is considered to have a high recovery potential as long as the limiting factors can be kept in check. In an effort to monitor the bighorn population, the California Department of Fish and Game has used radio collars and telemetry units; however this equipment requires extensive field work and few data points. In 2010, a new study using GPS satellite radio collars began; the GPS collars can collect more continuous data and allows scientists field time to be more efficient (National Park Service 2012). Limiting Factors for Bighorn Populations Disease The introduction of domestic sheep herds in the 19 th century brought with it the introduction of disease to the Sierra Nevada bighorn population (National Park Service 2012). Domestic sheep carry bacteria called Pasteurellaceae that causes respiratory infections in bighorns because they have no natural resistance. The impact of the respiratory diseases on bighorns varies, some cases are mild and others severe; however, both mild and severe respiratory infections in an adult bighorn can be passed on to the next generation of lambs causing fatal pneumonia. The transfer of the infection from parent to offspring causes depressed reproductive success and depleted populations. Lamb infection can occur for several years after an outbreak, making it extremely detrimental to the young bighorn population (see Figure 3) (Cahn, et al. 2011). Grazing allotments for domestic sheep that are near the Sierra Nevada bighorns habitat can potentially pose a risk of pathogen exposure, especially if they are not closely monitored (Cahn, et al. 2011). 3

4 Figure 3. In this figure graphs A and C show what respiratory disease outbreaks can do to the bighorn populations over time. A) Shows the affects of no, mild and severe respiratory disease outbreaks on a population. C) Shows how no disease, and outbreak after 6 years and an outbreak after 13 years affect the bighorn population with the impact being most drastic when the population is highest. (Cahn et al. 2011). Predation Mountain lions (Puma concolor) are the greatest predatory threat to the Sierra Nevada bighorns. Mountain lions affect the bighorns in two ways, first is predatory in the fact that they prey on the bighorns and second is that with reduced herd sizes from population fall throughout the years, the bighorns are not traveling to the lower winter grazing ranges that they had in the past for fear of mountain lions. With the smaller herd sizes the bighorns are more exposed and prone to be attacked in the open winter ranges, so the bighorns have been spending more winters at higher elevations where the conditions are harsher and the forage contains fewer nutrients. The 4

5 higher elevation winter ranges mean fewer bighorns are likely to survive the harsh mountain winters and fewer lambs are likely to be born in the spring (National Park Service 2012). Since the bighorn populations are too low to withstand normal predation, mountain lions have been removed from certain bighorn ranges to ensure the bighorns safety (U.S. Fish and Wildlife Service 2007) Low Population Numbers In 1995, barely 100 Sierra Nevada bighorn sheep were left; even today at around 400 individuals the numbers are still low (Sierra Nevada Bighorn Sheep Foundation). The low population work against the bighorn population until recovery can be made; low numbers are why the herds no longer go to the lower elevation winter ranges (National Park Service, 2012). Risk of predation because of low population is what keeps the sheep out of the lower mountain ranges but that results in decreased foraging efficiency (Schroeder et al 2010). Segregated herd groups (see Figure 1) coupled with low populations means smaller gene pools for the sheep and less breeding opportunities, therefore, lower lamb production rates (National Park Service 2012, U.S. Fish and Wildlife Service 2007). Small population numbers can be a perpetuating cycle causing the numbers to continue to dwindle in a downward spiral unless conservationists intervene and help recovery. Limited Distribution The spatial pattern in which the bighorn sheep live also negatively impacts their population numbers because they live in a small geographical region with segmented groups. Since the animals live in herd groups that remain in certain territories, they do not interbreed; the distribution results in a reduced gene pool. Bighorn habitat ranges were reduced in size and distribution when the population fell throughout the 20 th century since then, some sheep have been used as reintroduction stock to increase distribution (U.S. Fish and Wildlife Service 2007). Loss of Genetic Diversity The small population numbers of the herd groups results in a reduced gene pool and inbreeding causing the genetic diversity to decrease. Inbreeding can cause heterozygosity which may result in reduced fitness, loss of adaptability, and reduced lamb survival rates. There are also concerns of genetic drift between the different herds if they never come in contact, they may genetically drift to the point where they will become different subspecies (U.S. Fish and Wildlife Service 2007). Hypotheses: There are not any specific hypotheses with this proposal; however, the main purpose is to create GIS maps that display important information regarding the Sierra Nevada bighorn sheep. 5

6 These maps can be used to monitor the bighorn s recovery progress through time. Questions to be answered: Where are predators the biggest threat to the bighorns and possibly need to be removed? What bighorn deaths are a result of predation? Of accidents (falling or injuries from fighting rams)? Where have disease outbreaks occurred? How long ago and how severe were the outbreaks? What was the probable source of the pathogen? What are the movement patterns of female to male sheep (males are more likely to travel farther)? What types of grazing environments do males prefer over females? Where is the most nutrient rich forage for the bighorns? Are they likely to graze there? Why or why not? Has the nutritional value of forage changed in different locations over time? What is the genetic variation among bighorn groups? What herds are not genetically diverse and could be weak as a result of a poor gene pool? Data: A general map of the Sierra Nevada would be the base for all the GIS maps with any additional data put into layers to overlay the base map. By searching the internet, it s clear there are GIS and orthophoto maps of Sierra Nevada that could be used for this project. Much of the data needed for the additional layers is available in some form or another. Mountain lions have been tracked and deaths caused by predators or from accidents have been recorded. Data on disease outbreaks has also been collected over the years. An extensive report on male and female bighorns and their grazing patterns has been done and includes data on forage nutritional value over the seasons of the year. Also biomass information is available which can be coupled with forage nutrition. Many bighorns also have GPS radio collars that are collecting data that can be used to track their movements and give an idea of male versus female movement. The last map idea has the least amount of data available; genetic data on desert bighorn sheep to track colonization has been done and I propose doing the same for the Sierra Nevada Bighorn. Some data collected by fecal DNA extraction has been collected which may be enough to create a satisfactory GIS map of genetic diversity. All of the data needed to create a base for the GIS maps is present; some of the data may need to be digitized or converted into another form. Continued data collection will be most beneficial in creating comprehensive maps. Methods: 1. Create base map of Sierra Nevada. A DEM layer would be ideal to apply other data layers to. Also an orthophoto map would be beneficial for aesthetics. 2. Import other data layers including disease, predation, genetic diversity, male versus female movement and grazing habits, and forage nutrition. A layer of population and 6

7 distribution should be added just for comparison sake even though many of these maps already exist. 3. Different comparison rasters could be run using the data sets, such as male versus female disease infection rates or genetic diversity of different herd groups based on population or distribution. 4. Continue to introduce new data as it s collected to the GIS maps so they can be updated. Adding data over time also adds another dimension to analyze; it allows researchers to see the progress made by the animals whether it is positive or negative. The GIS data in this case is limited to the fact that it is primarily a display tool and most likely won t show researchers anything they don t already know. The maps will be beneficial in helping to identify and establish connections between different variables that are affecting the bighorn populations. Anticipated Results: The anticipated results are that by monitoring the predators, disease potentials, activity and overall well-being of the bighorns, any potential threats to the population can be quickly mitigated allowing the population to continue to increase. The GIS is a tool to keep a close eye on the population and its progress. Policy Applications: Results from ArcGIS analysis can alert researches if there is a threat to the bighorn population. An example would be if respiratory disease broke out as a result of contact with local domestic sheep herds, then the state can revoke grazing allotments close to bighorn habitat to protect the animals. Budget: ArcGIS software (desktop single): $1,500 ArcGIS professional: $20.00 hourly wage (Initial setup of maps (6 months): $20,800 Extended Project (3 years): $32,800) Computer: $ Most of the work could be done out of a home office but if including lab rental(this would include computers and ArcGIS software): $3125 per month = $30, Total (Initial setup project) = $71, (with GIS lab rental) $32, (working from home office). Total (Extended 3 year project) = $88, (with GIS lab rental) $49, (working from home office). *All totals were increased by 40% to compensate for institution overhead costs. This project is meant to piggyback on the U.S Fish and Wildlife Service recovery plan for the Sierra Nevada bighorn sheep; therefore, using much of the data collected by the government. 7

8 In 2007, U.S Fish and Wildlife Service proposed budget was $21.7 million over the course of 20 years. Timeframe: The timeframe on this project could vary depending on how long it takes for the bighorn population to recover and become more self-sufficient, and that is dependent on if GIS is a good way to monitor the populations. A temporary range for the project might be 3 years with new GIS and other field data being collected. Once all the initial data is collected it should only take a matter of months to create GIS maps that display the desired information. Any new data can be added as layers on existing maps and researchers can directly analyze the changes in population or factors from year to year. Stages: 1. Collect all data needed. Much of the data is already available, but some may need to be digitized or put into a format GIS and use. This may a few months to a year. 2. Put data into GIS. If done by a GIS analyst, this may only take a few weeks to a few months once the data is readily available because it entails putting the raw data into GIS and creating the appropriate maps. 3. Maintaining and updating the maps. As more data is continually collected on the bighorn populations, new data will be ready to be put onto the maps. This introduction of new data can be put in the existing GIS maps and new layers. The maintenance on the maps depends on how long the project is run for; if it is run for the 3 year time frame I suggest then after the initial setup someone can go in and input data which may take a week or two for a GIS professional every six months to a year. References: Cahn, M.L., Conner, M.M., Schmitz, O.J., Stephenson, T.R., Wehausen, J.D., and Johnson, H.E. (2011). Disease, Population Viability, and Recovery of Endangered Sierra Nevada Bighorn Sheep. Journal of Wildlife Management 75(8): BioOne. National Park Service Sierra Nevada Bighorn Sheep. Yosemite National Park, California. Retrieved from: Schroeder, C.A., Bowyer, R.T., Bleich, V.C., and Stephenson, T.R. (2010). Sexual Segregation in Sierra Nevada Bighorn Sheep, Ovis canadensis sierrae: Ramifications for Conservation. Arctic, Antarctic, and Alpine Research 42(4): BioOne. Sierra Nevada Bighorn Sheep Foundation. Endangerment. Founder: Wehausen, J.D. Retrieved from: 8

9 U.S. Fish and Wildlife Service Recovery Plan for the Sierra Nevada Bighorn Sheep. Sacramento, California. xiv pages. Retrieved from: 9

Photo by Mark Hebblewhite

Photo by Mark Hebblewhite BIGHORN DEMOGRAPHY AND OVERWINTER SURVIVAL The survival rate for radio-collared bighorn ewes during the 1 st quarter of 2008 was 90%; 1 ewe died following a fall and 4 mortalities