Richard B. Harris

Temporal, Spatial, and Environmental Influences on the Demographics of Grizzly Bears in the Greater Yellowstone Ecosystem

Abstract ABSTRACT During the past 2 decades, the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem (GYE) has increased in numbers and expanded in range. Understanding temporal, environmental, and spatial variables responsible for this change is useful in evaluating what likely influenced grizzly bear demographics in the GYE and where future management efforts might benefit conservation and management. We used recent data from radio-marked bears to estimate reproduction (1983–2002) and survival (1983–2001); these we combined into models to evaluate demographic vigor (lambda [λ]). We explored the influence of an array of individual, temporal, and spatial covariates on demographic vigor. We identified an important relationship between λ and where a bear resides within the GYE. This potential for a source–sink dynamic in the GYE, coupled with concerns for managing sustainable mortality, reshaped our thinking about how management agencies might approach long-term conservation of the species. Consequently, we assessed the current spatial dynamic of the GYE grizzly bear population. Throughout, we followed the information-theoretic approach. We developed suites of a priori models that included individual, temporal, and spatial covariates that potentially affected reproduction and survival. We selected our best approximating models using Akaikes information criterion (AIC) adjusted for small sample sizes and overdispersion (AICc or QAICc, respectively). We provide recent estimates for reproductive parameters of grizzly bears based on 108 adult (>3 years old) females observed for 329 bear-years. We documented production of 104 litters with cub counts for 102 litters. Mean age of females producing their first litter was 5.81 years and ranged from 4 to 7 years. Proportion of nulliparous females that produced cubs at age 4–7 years was 9.8, 29.4, 56.4, and 100%, respectively. Mean (±SE) litter size (n = 102) was 2.0 ± 0.1. The proportion of litters of 1, 2, and 3 cubs was 0.18, 0.61, and 0.22, respectively. Mean yearling litter size (n = 57) was 2.0 ± 0.1. The proportion of litters containing 1, 2, 3, and 4 yearlings was 0.26, 0.51, 0.21, and 0.02, respectively. The proportion of radio-marked females accompanied by cubs varied among years from 0.05 to 0.60; the mean was 0.316 ± 0.03. Reproductive rate was estimated as 0.318 female cubs/female/year. We evaluated the probability of producing a litter of 0–3 cubs relative to a suite of individual and temporal covariates using multinomial logistic regression. Our best models indicated that reproductive output, measured as cubs per litter, was most strongly influenced by indices of population size and whitebark pine (Pinus albicaulis) cone production. Our data suggest a possible density-dependent response in reproductive output, although perinatal mortality could have accounted for the correlation. We analyzed survival of cubs and yearlings using radiotelemetry of 49 unique female bears observed with 65 litters containing 137 dependent young. We documented 42 deaths: 32 cubs, 5 yearlings, and 5 that could have died as a cub or yearling. Using a nest survival estimator coded in Program MARK, our best model indicated that cub and yearling survival were most affected by residency in the GYE. Survival was highest for cubs and yearlings living outside Yellowstone National Park (YNP) but within the U.S. Fish and Wildlife Service (USFWS) Grizzly Bear Recovery Zone (RZ). Cubs and yearlings living inside YNP had lower survival rates, and those living outside the RZ had the lowest survival rates. Survival rates were negatively related to a population index, suggesting density dependence. Survival improved with higher whitebark pine seed production, greater winter severity, larger litter size, and higher female (mothers) age. We tested theories of sexually selective infanticide, but results were equivocal. We investigated factors influencing survival of subadult and adult grizzly bears using data from 323 radio-marked bears monitored for 5,989 months. Telemetry records were converted into monthly encounter histories, and survival was estimated using known fate data type in Program MARK. Bears were grouped into a study sample and conflict (bears specifically trapped because of conflict with humans) sample according to circumstance of capture and monitoring, with data from both contributing to survival estimates. A censored (C) data set included 69 documented mortalities but censored 22 bears with unknown fate. A second, assumed dead (AD), data set considered these 22 bears as mortalities. Most known mortalities (85.5%) were human caused, with 26 and 43 from the study and conflict samples, respectively. Mean annual survival, C F, for study sample female bears using C and AD data sets were C F = 0.950 (95% CI = 0.898–0.976) and AD F = 0.922 (95% CI = 0.857–0.995). Process standard deviation (SD) for study sample female bears was estimated at SDC = 0.013 and SDAD = 0.034. Our best models indicated that study sample bears survived better than conflict sample bears, females survived better than males, survival was lowest during autumn, and survival increased during years with good whitebark pinecone production. Bears with a higher proportion of annual locations outside the RZ exhibited poorer survival than individuals located more frequently inside YNP, the RZ, or both. Indices of winter severity, ungulate biomass, and population size, plus individual covariates, including presence of dependent young, prior conflicts with humans, and age class, were not important predictors of survival in our models. We documented a trend of increased survival through the study that was offset in recent years by lower survival of bears located more frequently outside the RZ. This result suggests that efforts to reduce female mortality initiated in 1983 were successful, and similar measures outside the RZ would improve the prospect for continued growth and expansion of the GYE grizzly bear population. To estimate sustainable mortality of the population, we produced trajectories of the GYE grizzly bear population under a range of survival rates of independent females (>2 years old) using an individual-based, stochastic simulation program and demographic data from radio-marked bears. We incorporated yearly (process) variation in survival rates as estimated from data after removing sampling variation. We summarized trajectories by mean λ and by probability of λ < 1, both within a 10-year period, and examined sensitivity of results by altering our initial assumptions to reflect uncertainty. Because process variation of female survival was low, λ decreased stochastically only slightly from that expected under a completely deterministic model. Uncertainty about mean cub and yearling survival rates was considerable, but because λ was relatively insensitive to these parameters, incorporating this uncertainty also lowered resulting trajectories only slightly. Uncertainty about independent female survival had a much larger effect on probability of population decline despite having little effect on expected λ. Under our current understanding of the GYE grizzly bear population dynamics, λ was independent of male survival rate; variation in male mortality produced only short-term effects on abundance and long-term effects on sex ratio. The appropriate mortality target for independent female bears depends on the risk of a population decline (i.e., λ < 1) that managers and the public are willing to accept. For the chance of a population decline to be ≤5% under conditions applying during 1983–2002, annual mortality of independent females would have to be ≤10%. Projections are useful only if viewed over a relatively short time frame because they were based solely on mean 1983–2002 conditions and because small samples make it difficult for managers to know the true mortality rate. To further explore the implications of geographic structure in female survival, we built an array of deterministic models using estimates of reproduction and survival from our best models. We calculated deterministic estimates of λ incorporating our residency covariate plus changes in whitebark pinecone production and winter severity. A source–sink dynamic is suggested for the GYE, with λ ≥ 1 inside YNP and the RZ but λ ≤ 1 outside the RZ. Such a source–sink dynamic requires new discussions about population management, mortality thresholds, and elimination of anthropogenic foods on the edge of the ecosystem. To enhance future management, we present food and population monitoring guidelines that should be considered in light of our findings. RESUMEN Durante las dos últimás décadas, la población del oso pardo (Ursus arctos) ha aumentado en números y se ha extendido geograficamente. Es útil entender los variables temporales, ambientales y espaciales que provocan este cambio, primero para evaluar las probables influencias sobre los demográficos del oso pardo en The Greater Yellowstone Ecosystem (el ecosistema mayor de Yellowstone) (GYE), y segundo para saber dónde dedicar los futuros esfuerzos que puedan beneficiar la conservación y el manejo de la población. Hemos utilizado datos de osos radiomarcados para medir y evaluar la reproducción (1983–2002) y la supervivencia (1983–2001). Hemos combinado estos datos y los hemos puesto en modelos para evaluar el vigor demográfico (lambda [λ]). Hemos explorado la influencia de una serie de covariables individuales, temporales, y espaciales sobre el vigor demográfico. Hemos identificado una relación importante entre λ y el lugar donde reside el oso dentro del GYE. La existencia potencial de una dinámica fuente-sumidero junto a la necesidad de manejar una tasa sostenible de mortalidad, nos llevaron a replantear la cuestión acerca de que cómo las agencias administrativas pueden abordar la conservación a largo plazo de la especie. Por consiguiente, hemos evaluado al actual dinámica espacial d

Productivity and early calf survival in the porcupine caribou herd

Concerns have been raised that displacement from traditional calving and postcalving areas by petroleum exploration may cause increased calf mortality in the Porcupine Caribou (Rangifer tarandus) Herd. Consequently, we determined productivity and early calf survival by frequently locating 23-53 radio-collared cows and 59-61 radio-collared calves from 1983 to 1985. Seventy-nine to 87% of the adult females gave birth each year, and 68-90% of calves were born within, or adjacent to, a coastal plain area proposed for petroleum leasing and development. Sixteen to 35% of the calves died by 25 June. Fifty-nine to 74% of calf mortality occurred within 48 hours of birth and involved a number of causes in addition to predation. Predation was the major cause of death after the first 48 hours, and mortality increased toward higher terrain away from the coastal plain

Reliability of Trend Lines Obtained from Variable Counts

Standard errors (SE) of trend lines arising from highly variable counts of animals are derived analytically given the variability of the counts, the number of years of trend monitoring, the number of replicate counts each year, and certain assumptions. Examples of the analytical solutions use and graphs of expected trend line variability are presented. When counts are highly variable, performing multiple counts each year is shown to be the only way to achieve precision of a population trend estimate within a short ( 100%. Goddards (1967) 18 replicate counts of black rhinoceros (Diceros bicornis) have a CV of 42%. A CV _50% is not uncommon with counts of rare species, such as grizzly bears; e.g., Reynolds (1974). Assuming lognormality, the a2 required for equation (3) is: 0.8

Argali Abundance in the Afghan Pamir Using Capture–Recapture Modeling From Fecal DNA

Abstract Estimating population size in a mark–recapture framework using DNA obtained from remotely collected genetic samples (e.g., feces) has become common in recent years but rarely has been used for ungulates. Using DNA extracted from fecal pellets, we estimated the size of an argali (Ovis ammon) population that was believed to be isolated from others within the Big Pamir Mountains, Afghanistan, an area where access was difficult and expensive. We used closed-capture models to estimate abundance, and Pradel models to examine closure assumptions, both as implemented in Program MARK. We also made visual counts of argali in the Big Pamirs, allowing comparison of count indices of abundance with modeled estimates. Our model-averaged estimate for female argali in the Big Pamir was 172 (95% CI  =  117–232), which was about 23% higher than our best assessment using uncorrected visual counts. However, mark–recapture models suggested that males were not a closed population; thus, we were unable to provide a meaningful estimate of overall population size. Males either suffered much higher mortality than females during the sampling period, or, more likely, males moved in and out of the Big Pamir area. Although information from DNA did not provide a clear overall population estimate, it suggested that the Big Pamir was not isolated from other argali populations, which could not have been confirmed with visual observations alone. Estimating argali population size using mark–recapture models and fecal DNA is feasible but may be too expensive for frequent monitoring of large and remote populations. Our study demonstrates the importance of sex identification and separate abundance estimation for each sex, especially if movement ecology differs by sex.

Status of Tibetan Plateau Mammals in Yeniugou, China

During September 2002, we conducted surveys focussing on the Tibetan plateau ungulate species in Yeniugou, Qinghai province, China, to compare abundance estimates with those from 1997 and the early 1990s. Wild yaks Bos grunniens, for which the area is named, evidently increased in number from about 1,200 to almost 1,700 animals. White-lipped deer Cervus albirostris, formerly quite rare in Yeniugou, also increased in number. Blue sheep Pseudois nayaur, Tibetan gazelle Procapra picticaudata and Tibetan wild ass Equus kiang remained almost steady or may have declined slightly. Tibetan antelope Pantholops hodgsoni which were historically resident in Yeniugou, but suffered a dramatic reduction during the 1990s, were completely absent in 2002. Argali Ovis ammon evidently continued to decline from their early 1990s level of approximately 250; we accounted for only 94 animals in 2002. We are uncertain of the causes for the argali decline, but the best supported hypothesis is that the recent increase in year-round presence of specific pastoral encampments has displaced argali groups from preferred seasonal foraging areas, causing permanent emigration, lower reproduction, higher mortality or some combination of the three. Poaching and disturbance from itinerant gold miners have declined in recent years, and most remaining species are fairing relatively well. The rapid development associated with the adjacent Qinghai-Tibet railroad has not yet affected the wildlife populations. Yeniugou contains probably the densest population of wild yaks in existence. Unfortunately, despite its obvious importance for Tibetan plateau fauna, Yeniugou still has no conservation-oriented management. Thus, wildlife populations are controlled indirectly by social and economic forces. Most Tibetan plateau mammals have limited tolerance for human activity; they persist in Yeniugou because people are still sparse. With the continued rapid economic development of nearby areas, the future of Yeniugous wildlife will not be secure until incentives are created for pastoralists, county officials and higher government authorities to favour maintaining its essentially wild and undeveloped character.

Population Growth of Yellowstone Grizzly Bears: Uncertainty and Future Monitoring

Abstract Grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem of the US Rocky Mountains have recently increased in numbers, but remain vulnerable due to isolation from other populations and predicted reductions in favored food resources. Harris et al. (2006) projected how this population might fare in the future under alternative survival rates, and in doing so estimated the rate of population growth, 1983–2002. We address issues that remain from that earlier work: (1) the degree of uncertainty surrounding our estimates of the rate of population change (λ); (2) the effect of correlation among demographic parameters on these estimates; and (3) how a future monitoring system using counts of females accompanied by cubs might usefully differentiate between short-term, expected, and inconsequential fluctuations versus a true change in system state. We used Monte Carlo re-sampling of beta distributions derived from the demographic parameters used by Harris et al. (2006) to derive distributions of λ during 1983–2002 given our sampling uncertainty. Approximate 95% confidence intervals were 0.972–1.096 (assuming females with unresolved fates died) and 1.008–1.115 (with unresolved females censored at last contact). We used well-supported models of Haroldson et al. (2006) and Schwartz et al. (2006a,b,c) to assess the strength of correlations among demographic processes and the effect of omitting them in projection models. Incorporating correlations among demographic parameters yielded point estimates of λ that were nearly identical to those from the earlier model that omitted correlations, but yielded wider confidence intervals surrounding λ. Finally, we suggest that fitting linear and quadratic curves to the trend suggested by the estimated number of females with cubs in the ecosystem, and using AICc model weights to infer population sizes and λ provides an objective means to monitoring approximate population trajectories in addition to demographic analysis.

Estimating abundance of mountain ungulates incorporating imperfect detection: argali Ovis ammon in the Gobi Desert, Mongolia

Abstract Estimating the density or abundance of mountain ungulates is difficult and rarely conducted in a statistically valid manner. The rough terrain they inhabit, their group-living habits, their relatively low density, and the difficulty of marking individuals all contribute to making rigorous estimates of abundance logistically difficult. Raw (uncalibrated) counts are usually reported, and although their drawbacks are often acknowledged, biases are rarely quantified. In September 2009, we took advantage of the presence of a radio-marked sample of argali Ovis ammon in the Ikh Nart Nature Reserve in south-central Mongolia, as well as the areas comparatively forgiving topography to estimate abundance simultaneously using two independent methods: distance sampling and mark-resight sampling. Distance sampling produced an abundance estimate of 539 (95% CI: 196-1,081) argali within a ∼ 330 km2 study area on the same day that we visually tallied 189 animals. Mark-resight sampling using the Poisson log-normal model yielded an estimate of 747 (95% CI: 484-1,009) argali when we observed, at most, 223 animals in any given day. Although both were imprecise, their similarity increases our confidence that neither estimator was highly biased. Because of budget or logistical restrictions, uncalibrated counts of mountain ungulates are often the only alternative. They should be viewed cautiously, however, and when possible, more rigorous approaches to estimating abundance should be taken.

Incentives toward conservation of argali Ovis ammon: a case study of trophy hunting in western China

We investigated management of wildlife, habitat and the hunting programme in Aksai County, Gansu Province, Peoples Republic of China, during 1997–2000. Argali Ovis ammon is the focal species both for conservation and hunting. The hunting programme is intended to produce incentives to conserve wildlife and habitat. Poaching, a serious concern throughout western China, has been reduced in recent years in Aksai. Wildlife population trends are unknown because standardized surveys were begun only in 2000. Threats to argali in Aksai include livestock grazing, placer gold mining, and development of a dam, reservoir and aqueduct. The number of hunters participating in the programme ( c . 3 per year) could provide considerable funding ( c .

Status and trends of Tibetan plateau mammalian fauna, Yeniugou, China

60,000 per year), but the allocation of these funds within China has provided too little for conservation at the local level, thus undermining the intended incentive system. Because local wildlife protection officials have been denied both funding and authority to deal with threats to the wildlife, the programmes contribution to conservation has been minor. We recommend that hunters pay fees directly to county-level staff, thus increasing the proportion of funds retained at county-level, and that this added income is used to obtain wildlife grazing rights on important seasonal habitats for argali. These changes would promote local wildlife conservation without the need for additional external funding.

Herbivory and Competition of Tibetan Steppe Vegetation in Winter Pasture: Effects of Livestock Exclosure and Plateau Pika Reduction

Abstract We conducted surveys focusing on the unique and vulnerable ungulate species in Yeniugou, Qinghai province, China, during September 1997 to compare population estimates with those from the early 1990s. The status of two ungulate species appeared essentially unchanged since 1990–1992: wild yak Bos grunniens (about 1200 to 1300 animals) and Tibetan gazelle Procapra picticaudata. The status of one ungulate species, the white-lipped deer Cervus albirostris, appeared to improve, from a very few to close to 100. We are unsure how the status of the Tibetan wild ass Equus kiang compares with that of the early 1990s. The status of three species declined during the period: blue sheep Pseudois nayaur and argali Ovis ammon declined slightly (possibly due to a weather event), and the Tibetan antelope Pantholops hodgsoni declined dramatically (probably due primarily to poaching), from over 2000 estimated in 1991 to only two seen during 1997. Poaching of antelope has become a serious problem throughout the Tibetan plateau in recent years, and this survey provides evidence that an entire subpopulation can disappear (either through mortality, movement away from human disturbance or a combination) within a relatively short time-frame. That some species (e.g. wild yak, white-lipped deer) continue to thrive in Yeniugou is heartening, but even they remain vulnerable to market-driven poaching.