Adult Female Survival Rates Research Articles

Assessment of optimal blood exposure time at 37 °C during in vitro tsetse flies feeding for quality production in mass-rearing colonies.

Control of African animal trypanosomosis is implemented through an integrated control strategy, with the sterile insect technique (SIT) as one of its components. The SIT requires mass rearing of tsetse fly colonies using an in vitro feeding system. The exposure of blood at 37 °C on heating plates over time can have an impact on the quality of fly productivity. In this study, we investigated the survival and fecundity of adult tsetse flies fed at 37 °C on 8 blood exposure times ranging from 30 min to 4 h with increments of 30 min (treatment 1, flies were fed 30 min after exposure to blood at 37 °C; treatment 2, 1 h and so on until treatment 8 [4 h after]) in order to determine the optimal exposure time. In addition, bacterial growth in blood from each treatment was assessed by agar culture at 37 °C for 72 h. The results showed that the adult female survival rates were similar regardless of the treatment. For males, only those of treatment 1 (30 min) showed a marginal lower survival than those of treatments 7 and 8 fed after 3 h 30 min and 4 h of blood exposure, respectively. Over the 4-h interval of blood exposure at 37 °C, the results showed that the number of pupae produced per initial female and pupal weight tended to increase with exposure time, but the differences were not significant. We discuss the implications of these results on tsetse mass rearing for the SIT program.

Survival effects of antibiotic exposure during the larval and adult stages in the West Nile virus vector Culex pipiens.

The ability of mosquitoes to transmit a pathogen is affected, among other factors, by their survival rate, which is partly modulated by their microbiota. Mosquito microbiota is acquired during the larval phase and modified during their development and adult feeding behavior, being highly dependent on environmental factors. Pharmaceutical residues including antibiotics are widespread pollutants potentially being present in mosquito breeding waters likely affecting their microbiota. Here, we used Culex pipiens mosquitoes to assess the impact of antibiotic exposure during the larval and adult stages on the survival rate of adult mosquitoes. Wild-collected larvae were randomly assigned to two treatments: larvae maintained in water supplemented with antibiotics and control larvae. Emerged adults were subsequently assigned to each of two treatments, fed with sugar solution with antibiotics and fed only with sugar solution (controls). Larval exposure to antibiotics significantly increased the survival rate of adult females that received a control diet. In addition, the effect of adult exposure to antibiotics on the survival rate of both male and female mosquitoes depended on the number of days that larvae fed ad libitum in the laboratory before emergence. In particular, shorter larval ad libitum feeding periods reduced the survival rate of antibiotic-treated adult mosquitoes compared with those that emerged after a longer larval feeding period. These differences were not found in control adult mosquitoes. Our results extend the current understanding of the impact of antibiotic exposure of mosquitoes on a key component of vectorial capacity, that is the vector survival rate.

Regional variability in pregnancy and survival rates of Rocky Mountain bighorn sheep

AbstractIn the Rocky Mountains, bighorn sheep restoration has been only marginally effective; this iconic wilderness species currently exists at a fraction of their historic abundance and often in fragmented and small populations. To inform bighorn sheep conservation and restoration efforts, it is critical to understand sources of variation in key vital rates. Our objectives were to characterize the spatiotemporal variations and factors affecting survival and pregnancy rates of bighorn sheep (Ovis canadensis) using data from 19 bighorn sheep populations in Montana and Wyoming that occupied diverse landscapes ranging from the Northern Great Plains to the Rocky Mountains. We used a hierarchical modeling approach to estimate survival and pregnancy rates of adult females and identify the important intrinsic and environmental factors affecting these vital rates. Survival of prime‐aged animals was relatively high and stable, and pregnancy rates for prime‐aged animals showed more overall variation in response to intrinsic and extrinsic factors. Summer growing season, as indexed by integrated NDVI, positively influenced the probability of pregnancy and winter survival. This highlights the important relationship between summer growing season conditions and bighorn sheep physiological status. An index of mountain lion population abundance was related weakly to winter survival of bighorn sheep, with mountain lion abundance on winter ranges negatively affecting winter survival. Our results regarding the distribution of the estimated probabilities of pregnancy and survival, and the identification of factors associated with regional variability in these vital rates provide a foundation for understanding the dynamics of bighorn sheep populations in the Rocky Mountains. The importance of summer growing season conditions suggests management efforts should focus on maintaining and improving nutritional resources on bighorn sheep summer ranges, in efforts to enhance the condition of animals entering the breeding season and nutrient‐limited winter season. Although we document nontrivial changes in both pregnancy and winter survival rates associated with environmental variation, our results broadly support the dominant paradigm of ungulate demography insofar as survival rates of adult females were relatively higher and had less variation than pregnancy rates.

Demographic parameters of southern right whales off South Africa

Aerial counts of right whale cow-calf pairs on the south coast of South Africa between 1971 and 1998 indicate an annual instantaneouspopulation increase rate of 0.068 per year (SE = 0.004) over this period. Annual photographic surveys since 1979 have resulted in 901resightings of 550 individual cows. Observed calving intervals ranged from 2-15 years, with a principal mode at 3 years and secondarymodes at 6, 9 and 12 years, but these make no allowance for missed calvings. Using the model of Payne et al. (1990), a maximum calvinginterval of 5 years produces the best fit to the data giving a mean calving interval of 3.12 years (95% confidence interval: 3.07, 3.17). Thesame model produces an estimate for adult female survival rate of 0.983 (95% CI: 0.972, 0.994). The Payne et al. (1990) model is extendedto incorporate information on the observed ages of first reproduction of grey-blazed calves, which are known to be female. This allows theestimation of age at first parturition (median 7.88 years 95% CI 7.17, 9.29). Updates of estimates and confidence intervals for the otherdemographic parameters are: adult female survival rate 0.986 (0.976, 0.999); first year survival rate 0.913 (0.601, 0.994) and instantaneouspopulation increase rate 0.071 (0.059, 0.082). These biological parameter estimates are shown to be compatible with the observed increaserate of the population without the need to postulate immigration.

Adult Survival of Common Eiders in Maine

Although most species of sea ducks are poorly studied, much is known about the population dynamics of the American race of Somateria mollissma dresseri (Common Eider). Although Common Eiders typically have high adult survival and low recruitment rates, their populations in Maine have declined since the early 1990s. Wildlife managers hypothesized this decline was due to reduced adult survival; therefore, they decreased daily bag limits in Maine in 1999 and 2009 to increase local populations. The goals of this project were to assess (a) whether survival rates of adult females captured while nesting varied between historical estimates (1943–1993) and recent estimates (2000–2012), (b) whether survival rates increased from 2000–2009 after the initial harvest restrictions were implemented in 1999, and (c) determine if estimates of survival rates of adult males and females captured while molting differed from estimates of adult females captured while nesting. We used mark–recapture models to estimate survival rates of Common Eiders we banded in Maine (nesting females [n = 2340] from 2000 to 2012; molting males [ n = 4366] and molting females [n = 4952] from 2000 to 2009). We found no difference in survival of nesting females based on historical (mean ± SE = 0.9003 ± 0.0841) and recent estimates (0.90 ± 0.015). Although we observed annual fluctuations in survival, survival rates did not increase following the implementation of harvest restrictions. Mean annual survival rates were similarly high for molting females (0.894 ± 0.0205) and nesting females, but lower for molting males (0.855 ± 0.0128). Lower survival rates of adult males may reflect the preference by US hunters to selectively harvest adult males. Overall mean recovery rates of banded birds were low (females: 0.037 ± 0.00043, males: 0.0226 ± 0.0006). We hypothesize that current harvest rates may be influencing decreased survival of adult males to some extent.

Cold hardiness in immature stages and adults in the adult‐diapausing spider mite Stigmaeopsis longus

AbstractThe cold hardiness of arthropods is an important characteristic associated with overwintering success. Cold‐tolerant stages affect overwintering strategy, especially in arthropods that continuously feed on evergreen host plants in temperate regions. However, cold hardiness to mildly low temperature is rarely investigated. In the present study, we estimate the stage‐specific cold hardiness of a population of the spider mite Stigmaeopsis longus (Saito) (Acari: Tetranychidae) occurring on evergreen Sasa bamboo in a temperate area (Kochi City, southwestern Japan). Individuals of each stage developing under diapause‐inducing conditions (LD 10 : 14 h at 20 °C) are maintained at 4 °C (approximating the mean daily minimum temperature for December in Kochi City) for 30 days (eggs are cooled immediately, without short‐day development first). They are then returned to the initial conditions to assess survival rates. The survival rate of adult females (i.e. the diapausing stage) is high (99.5%), as is that of adult males and deutonymphs of both sexes (84.2–98.7% and 89.7–89.8%, respectively). The survival rate of mobile immature stages tends to increase toward adulthood in both sexes, whereas the survival rate of the eggs and quiescent stages is extremely low (16–23% and 0–20%, respectively). The poor cold hardiness of the eggs and quiescent stages presumably prevents the normal development of immature individuals during winter.

Estimating population extinction thresholds with categorical classification trees for Louisiana black bears.

Monitoring vulnerable species is critical for their conservation. Thresholds or tipping points are commonly used to indicate when populations become vulnerable to extinction and to trigger changes in conservation actions. However, quantitative methods to determine such thresholds have not been well explored. The Louisiana black bear (Ursus americanus luteolus) was removed from the list of threatened and endangered species under the U.S. Endangered Species Act in 2016 and our objectives were to determine the most appropriate parameters and thresholds for monitoring and management action. Capture mark recapture (CMR) data from 2006 to 2012 were used to estimate population parameters and variances. We used stochastic population simulations and conditional classification trees to identify demographic rates for monitoring that would be most indicative of heighted extinction risk. We then identified thresholds that would be reliable predictors of population viability. Conditional classification trees indicated that annual apparent survival rates for adult females averaged over 5 years () was the best predictor of population persistence. Specifically, population persistence was estimated to be ≥95% over 100 years when , suggesting that this statistic can be used as threshold to trigger management intervention. Our evaluation produced monitoring protocols that reliably predicted population persistence and was cost-effective. We conclude that population projections and conditional classification trees can be valuable tools for identifying extinction thresholds used in monitoring programs.

Robustness of adult female survival maintains a high-density sika deer (Cervus nippon) population following the initial irruption

Context Irruption of large herbivore populations is characterised by three distinct phases: (1) an exponential increase in population to a peak abundance; (2) a population crash; and (3) a second increase to another population peak, typically lower than the first peak of abundance. However, there has been little study of age- and sex-specific factors that affect the post-initial irruption interactions with food sources. Aims We aimed to investigate annual survival rates of sika deer (Cervus nippon Temminck, 1838) in the sequent irruption of a population on Nakanoshima Island, Lake Toya, Japan, with a chronically high density during the period 2002–12. Methods Survival monitoring data were obtained for 219 individuals (93 males and 126 females) using radio-collars. Annual survival was quantified, and related factors, i.e. deer abundance and winter severity, were determined by model selection using Akaike information criterion values. Key Results The results showed that annual survival rates across sexes and age classes (fawn, yearling, prime-aged, old) decreased with increasing population density, snow depth and winter precipitation. Winter severity had a greater effect on adult survival than density regulation. Nevertheless, female adult survival was maintained at a high level, with a mean of 0.84 (95% CI: 0.80–0.88). Key conclusions Robust survival rates for adult females might contribute to the maintenance of a high-density sika deer population in the post-initial irruption. Implications We suggest that in the absence of predation and hunting, sika deer population is not able to self-regulate to the density level that avoids an irreversible impact on plants.

Survival of desert mule deer fawns in central Arizona

Abstract Desert mule deer (Odocoileus hemionus eremicus) densities in central Arizona are below historic levels, likely due to neonatal mortality influencing desert mule deer population dynamics. However, no direct assessments have been made into causes and timing of neonatal mortalities in central Arizona. The objectives of our study were to determine the causes and timing of mortalities of desert mule deer fawns, estimate the annual survival rate of adult females and fawns, and quantify predator effects on fawn survival. In 2007 and 2008 we captured 52 adult female desert mule deer and equipped pregnant females with vaginal implant transmitters to aid in capturing fawns. We performed survival analyses using Program MARK and compared competing models with Akaike's information criterion. We captured 44 desert mule deer fawns; summer survival was 0.432 (95% CI = 0.292–0.584) and annual fawn survival was 0.071 (95% CI = 0.013–0.303). Predation accounted for 64% of fawn mortality. Probability of fawn surviva...

Sex‐related variation in the vulnerability of wandering albatrosses to pelagic longline fleets

AbstractThe population of wandering albatrosses Diomedea exulans at South Georgia is decreasing because of bycatch in longline fisheries. Until at least the early 1990s, the survival rate of females was lower than males, consistent with the adult female‐biased bycatch reported for fisheries operating around the Brazil‐Falklands Confluence (BFC). Here we use extensive tracking data (1990–2012) from breeding birds at South Georgia to investigate overlap with longline fishing effort reported to the International Commission for the Conservation of Atlantic Tunas (ICCAT). Using data from multiple years, we conclude that breeding females are at higher risk than males from all the main pelagic longline fleets in the south‐west Atlantic. Our overlap index (based on fishing effort and bird distributions) correlated positively with numbers of ringed birds reported dead on longliners, indicating that the metric was a good proxy of bycatch risk. The consistent sex bias in overlap across years, and the likely resulting sex‐biased mortality, could account for lower adult female survival rate at the colony. The risk from fisheries changed seasonally; both sexes overlapped with pelagic longline effort during incubation (January–March), and particularly during post‐brood chick‐rearing (May–December), whereas overlap was negligible during brooding (April). The highest percentage of overlap was with the Taiwanese fleet, then vessels flagged to Brazil, Uruguay, Spain, Japan and Portugal. Females were consistently at greatest risk in the BFC region, whereas males showed lower and more variable levels of overlap with fisheries from 35 to 45°S. Our results have important implications for management of ICCAT longline fisheries and conservation of this highly threatened albatross population.

Variation in mallard vital rates in Canadian Aspen Parklands: The Prairie Habitat Joint Venture assessment

ABSTRACTThe Prairie Habitat Joint Venture (PHJV) delivers conservation programs for the Canadian portion of the Prairie Pothole Region under the North American Waterfowl Management Plan. The PHJV Assessment was designed to evaluate biological assumptions and effectiveness of PHJV conservation activities. Our objectives were to 1) test whether waterfowl reproductive success increased in response to the full suite of PHJV habitat treatments, and 2) quantify the relationships between mallard (Anas platyrhynchos) vital rates and landscape variables. We focused on examining the association of mallard vital rates with covariates measured at the study‐area scale. We collected information on vital rates from 3,214 radio‐marked female mallards at 27 study areas mainly throughout the Aspen Parkland ecoregion of Manitoba, Saskatchewan, and Alberta in 1993–2000. We used a modeling framework and information‐theoretic techniques to test hypotheses about putative effects of environmental covariates on adult female and duckling survival, nesting effort, and nest survival. Additionally, we constructed a stage‐based matrix projection model of mallard population growth (λ) to estimate the sensitivities of population growth rates to variation in vital rates. Nest survival was positively related to the amount of herbaceous vegetation on study areas and total precipitation for the 12 months prior to nesting. Nesting effort was positively related to wetland inundation in July. Duckling survival was positively related to the proportion of seasonal wetlands holding water in July and negatively related to the number of days in June and July when the minimum air temperature dropped below 10° C. Adult female survival rate was positively related to both the proportions of grassland and wetland habitats measured at the study‐area scale (65 km2), though these factors interacted such that the positive relationship with proportion of wetlands was strongest on study sites with high proportions of grassland. The stage‐based projection model constructed using mean vital rates indicated that populations were declining (meanλ = 0.95, medianλ = 0.98, 5th percentile = 0.68, 95th percentile = 1.38). Variance‐stabilized sensitivities indicated that population growth was most responsive to variation in vital rates for after‐second‐year birds and that nest survival was the single vital rate to which populations were most sensitive. A prospective simulation revealed that, as expected, sensitivity to nest survival is likely to decrease at higher levels of nest survival. Despite evidence that nest survival was higher in PHJV habitat treatments than surrounding habitats, our a priori PHJV treatment index was unrelated to mallard vital rates estimated at the 65‐km2scale. Although mallard populations were affected by several weather variables and land uses, efforts to increase populations should focus on improving nest survival rates, which currently are below approximately 30%. © 2014 The Wildlife Society.

Survival rates of cougars in Oregon from 1989 to 2011: A retrospective analysis

ABSTRACTCougar (Puma concolor) management in Oregon is unique because hunting cougars with dogs was allowed through the 1994 hunting season, but thereafter Ballot Initiative Measure 18 prohibited the use of dogs to pursue cougars. Since 1995, hunting seasons have become increasingly longer with more tags sold. The effects of changing management structure on survival rates and causes of mortality of cougars are not well understood. We investigated survival and documented causes of mortality of radiocollared cougars at 3 study areas in Oregon from 1989 to 2011 under contrasting management strategies. The Catherine Creek (1989–1996) and Jackson Creek (1993–2002) studies overlapped the prohibition of hunting cougars with dogs, and the Wenaha, Sled Springs, and Mt. Emily (WSM) study was conducted from 2002 to 2011 when hunting cougars with dogs was illegal. Hunting mortality was the most common cause of death for sub‐adult and adult cougars in Catherine Creek pre‐ (18 of 23 mortalities) and post‐Measure 18 (1 of 2 mortalities) and WSM (24 of 53 mortalities) study areas in northeast Oregon. In contrast, natural mortality was the most common cause of death of sub‐adults and adults at the Jackson Creek (25 of 38 mortalities) study area in southwest Oregon, but hunting mortality was most common prior to the passage of Measure 18 (3 of 3 mortalities). We estimated annual survival rates of cougars using known fate models in Program MARK. Annual survival rates of adult males were lowest at Catherine Creek prior to the passage of Measure 18 ( = 0.57; 95% CI = 0.39–0.73) and increased after Measure 18 ( = 0.86; 95% CI = 0.79–0.92), which were similar to those rates observed at Jackson Creek pre‐ and post‐Measure 18 ( = 0.78; 95% CI = 0.65–0.88) and WSM ( = 0.82; 95% CI = 0.69–0.91). Regardless of hunting regulations, annual survival rates of adult females was similar among study areas (Catherine Creek pre‐ and post‐Measure 18 [ = 0.86; 95% CI = 0.79–0.92]; Jackson Creek pre‐ and post‐Measure 18 [ = 0.85; 95% CI = 0.77–0.91]; WSM [ = 0.85; 95% CI = 0.76–0.90]). At Jackson Creek pre‐ and post‐Measure 18 and WSM, sub‐adult males (1–3 years) had significantly lower survival than sub‐adult females, but survival rates of males and females were similar by age 4 or 5 years. At WSM, survival declined for both sexes at older ages (8–13 years), but this decline was not observed at Jackson Creek pre‐ or post‐Measure 18. The effect of increasing age on cougar survival should be considered when using survival rates to estimate population growth rates. We did not detect an effect of age on cougar survival at the Catherine Creek study area pre‐ or post‐Measure 18, which we attributed to selective harvest of prime‐aged, male cougars prior to the passage of Measure 18 and lack of mortality post‐Measure 18. Managers should understand local sources of mortality when setting harvest regulations because sources of mortality may vary widely within and among jurisdictions, even if management practices are similar. Because of low hunter success rates when hunting cougars without dogs, survival rates of cougars managed under this hunting regime should be substantially higher than areas where use of dogs is legal. This suggests the ability of managers to effectively manipulate survival rates of cougars to meet population management objectives will be dependent on available hunting methods. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Can managers compensate for coyote predation of white‐tailed deer?

ABSTRACTMany studies have documented that coyotes (Canis latrans) are the greatest source of natural mortality for white‐tailed deer (Odocoileus virginianus) neonates (<3 months old). With the range expansion of coyotes eastward in North America, many stakeholders are concerned that coyote predation may be affecting deer populations adversely. We hypothesized that declines in neonate survival, perhaps caused by increasing coyote predation, could be offset by adjusting or eliminating antlerless harvest allocations. We used a stochastic, age‐based population simulation model to evaluate combinations of low neonate survival rates, severe winters, and low adult deer survival rates to determine the effectiveness of reduced antlerless harvest at stabilizing deer populations. We found that even in regions with high winter mortality, reduced antlerless harvest rates could stabilize deer populations with recruitment and survival rates reported in the literature. When neonate survival rates were low (25%) and yearling and adult female survival rates were reduced by 10%, elimination of antlerless harvests failed to stabilize populations. Our results suggest increased deer mortality from coyotes can be addressed through reduced hunting harvest of adult female deer in most circumstances throughout eastern North America. However, specific knowledge of adult female survival rates is important for making management decisions in areas where both neonate and adult survival may be affected by predation and other mortality factors. © 2014 The Wildlife Society.

Effects of suspended sediments on reproductive responses of Paracalanus sp. (Copepoda: Calanoida) in the laboratory

The ingestion rate, egg production, egg-hatching success and survival rate of adult female copepods, Paracalanus sp., in relation to a suspended sediment concentration gradient (control: 0 mg L, low: 10 mg L, middle: 30 mg L and high: 100 mg L) were examined in the laboratory under two concentrations (1 10 and 1 10 cells mL) of the dinoflagellate Prorocentrum minimum to understand the impacts of turbidity on the reproductive responses. Ingestion rates under both phytoplankton concentrations were significantly lower at high level of suspended sediments than at the control level. The egg production rate at the low phytoplankton concentration also decreased with increasing suspended sediment concentration, but there was no effect of suspended sediment on egg production at the high phytoplankton concentration. Egg-hatching success was relatively high at .90%; thus, there was no deleterious effect of suspended sediments on egg viability. The survival rate of adult females decreased with time in all treatments, indicating no negative effects of suspended sediments on the mortality of female copepods. These results suggest that higher concentrations of suspended sediments might have negative effects on copepod recruitment in the field. Feeding efficiency on phytoplankton decreased in the presence of suspended sediments, thus potentially decreasing the copepod egg production rate. However, the negative effects may be lessened if the copepod ingests more food in terms of both quality and quantity in favorable food environments.

EFFECT OF DIFFERENT TYPES OF FOOD ON DEVELOPMENT AND FECUNDITY OF PREDACIOUS MITE NEOSEIULUS BELLINUS WOMERSLEY (ACARI: PHYTOSEIIDAE)

Phytoseiids mites are known as cosmopolitan predators throughout the world. They have a wide range of natural foods, though preferences may be shown for certain foods on which development may be faster and egg production greater than on others. Data herein showed that Neosiulus bellinus was able to complete development and reproduce when fed on eggs of Tetranychus urticae Koch and AD-1 with a survival rate reached 90 and 60 % respectively. However, it could not survive when fed on AD-2 and AD-3 artificial diets. On the other hand, Adult female longevity of phytoseiid mite N. bellinus was found to be longer when fed on eggs of spider mites than the experimental diet AD-1 as was the oviposotion period. Female fecundity was also greatest on eggs of spider mite. While, adult was short lived when no food source offered. Moreover, the survival rates of adult females fed AD-1 after long term maintenance10, 20, and 30 days was 35, 21 and 6 %, respectively.

Survival and harvest‐related mortality of white‐tailed deer in massachusetts

AbstractWe monitored 142 radiocollared adult (≥1.0 yr old) white‐tailed deer (Odocoileus virginianus) in 3 study areas of Massachusetts, USA, to estimate annual survival and mortality due to legal hunting. We then applied these rates to deer harvest information to estimate deer population trends over time, and compared these to trends derived solely from harvest data estimates. Estimated adult female survival rates were similar (0.82–0.86), and uniformly high, across 3 management zones in Massachusetts that differed in landscape composition, human density, and harvest regulations. Legal hunting accounted for 16–29% of all adult female mortality. Estimated adult male survival rates varied from 0.55 to 0.79, and legal hunting accounted for 40–75% of all mortality. Use of composite hunting mortality rates produced realistic estimates for adult deer populations in 2 zones, but not for the third, where estimation was hindered by regulatory restrictions on antlerless deer harvest. In addition, the population estimates we calculated were generally higher than those derived from population reconstruction, likely due to relatively low harvest pressure. Legal harvest may not be the dominant form of deer mortality in developed landscapes; thus, estimates of populations or trends that rely solely on harvest data will likely be underestimates. © 2011 The Wildlife Society.

Demographic consequences of anthropogenic influences: Florida black bears in north-central Florida

Anthropogenic habitat fragmentation poses a serious threat to conservation of large carnivores, due to their extensive movements and potential conflicts with humans. We studied the population ecology of Florida black bears ( Ursus americanus floridanus) for 6 years in two study areas in north-central Florida: Ocala National Forest (ONF), a contiguous forested habitat, and an adjacent residential community of Lynne, a fragmented habitat with substantial human activities. We estimated age-specific survival and fecundity rates of bears using data from radio-collared bears, and parameterized and analyzed stage-structured matrix population models for the two study sites and also for data pooled from both sites. Annual survival rates of adult females were lower in Lynne (0.776 ± 0.074) than in ONF (0.966 ± 0.023). While cub survival rates were higher in Lynne (0.507 ± 0.135) than in ONF (0.282 ± 0.109), the rates at both sites were substantially lower than those reported for other black bear populations. Age-specific fecundities did not vary between sites. The asymptotic population growth rate for ONF was greater than one, whereas that for Lynne was less than one. Our results suggest that anthropogenic influences (primarily road density and vehicular traffic, through their effect on adult survival) can substantially affect the population dynamics of Florida black bears and other large carnivores with large home ranges. We recommend efforts such as constructing highway underpasses, which could reduce road-related mortalities, to ensure long-term persistence of Florida black bears facing threats from rapidly increasing human influences.

Predator-Specific Mortality of Pronghorn on Yellowstone's Northern Range

Yellowstone National Park supports a small population (<300) of pronghorn (Antilocapra americana). Some individuals migrate during summer to areas characterized by reduced visibility, mixed habitat types, and a diverse predator community. Across areas selected by migratory and nonmigratory pronghorn, we documented cause-specific mortality of adults and fawns and assessed relative risk of predation by various predators. Coyotes (Canis latrans) accounted for 56% of adult predation and up to 79% of fawn predation. Cougars (Puma concolor) and wolves (Canis lupus) accounted for additional predation of adults, while cougars, black bears (Ursus americanus), and Golden Eagles (Aquila chrysaetos) were documented killing fawns on rare occasions. Our results suggest that even when pronghorn are in the presence of multiple predator species, coyote predation on adults and fawns may predominate for populations inhabiting shrubsteppe habitat. However, the risk of predation by sympatric predators, particularly cougars, may be high for female pronghorn selecting mixed cover types during migration or for birthing purposes. While the direct effect of wolves on overall mortality was low, wolves may indirectly influence survival rates of adult females and fawns by altering the behavior and space use of sympatric predators, particularly coyotes.

Modelling the effects of fertility control on koala–forest dynamics

Summary Koala Phascolarctos cinereus populations sometimes exhibit eruptive dynamics, increasing to peak abundance and then crashing to low abundance. This dynamic is considered unacceptable because koalas die from starvation and food trees are killed by defoliation. There is concern that such dynamics may be occurring at a number of sites in south‐eastern Australia. The only management option is fertility control of females. We constructed a simulation model of koalas interacting with their food supply (manna gum Eucalyptus viminalis) in Mount Eccles National Park, Victoria, Australia. The amount of manna gum leaves consumed changed the survival and fecundity rates of koalas, and the amount of leaves removed changed the survival and transition rates of manna gums. Without fertility control the koala population was predicted to increase to peak abundance within 10–18 years before crashing. The predicted dynamics of manna gum were more variable but abundance increased in most simulations for up to c. 5 years before declining to c. 25% of peak abundance within 20–30 years and then increasing subsequently. The maximum rate of koala population decline was an important determinant of the interaction between koalas and manna gum. The best management strategy that was analysed involved estimating the number of unsterilized females in the population annually and then sterilizing a variable number to maintain a population of 1000 koalas: this strategy generated the least decline in manna gum at a consistently low cost. However, there was a delay between imposing fertility control and consequent reduction in koala abundance because of high adult female survival rates. Hence manna gum was predicted to decline for 5–10 years before increasing. Synthesis and applications. Our results highlight important time‐lags between implementing fertility control, reducing the abundance of a herbivore with high survival rates and subsequent changes in the abundance of its food supply. Our model is useful for understanding how controlling ‘overabundant’ herbivores impacts upon the dynamics of both the herbivore and its food supply.

Dynamics of Newly Established Elk Populations

Abstract: The dynamics of newly established elk (Cervus elaphus) populations can provide insights about maximum sustainable rates of reproduction, survival, and increase. However, data used to estimate rates of increase typically have been limited to counts and rarely have included complementary estimates of vital rates. Complexities of population dynamics cannot be understood without considering population processes as well as population states. We estimated pregnancy rates, survival rates, age ratios, and sex ratios for reintroduced elk at Theodore Roosevelt National Park, North Dakota, USA; combined vital rates in a population projection model; and compared model projections with observed elk numbers and population ratios. Pregnancy rates in January (early in the second trimester of pregnancy) averaged 54.1% (SE = 5.4%) for subadults and 91.0% (SE = 1.7%) for adults, and 91.6% of pregnancies resulted in recruitment at 8 months. Annual survival rates of adult females averaged 0.96 (95% CI = 0.94‐0.98) with hunting included and 0.99 (95% CI = 0.97‐0.99) with hunting excluded from calculations. Our fitted model explained 99.8% of past variation in population estimates and represents a useful new tool for short‐term management planning. Although we found no evidence of temporal variation in vital rates, variation in population composition caused substantial variation in projected rates of increase (Λ = 1.20‐1.36). Restoring documented hunter harvests and removals of elk by the National Park Service led to a potential rate of Λ = 1.26. Greater rates of increase substantiated elsewhere were within the expected range of chance variation, given our model and estimates of vital rates. Rates of increase realized by small elk populations are too variable to support inferences about habitat quality or density dependence.