Survival and cause-specific mortality of moose calves in Northeastern Minnesota

Ungulate reproductive success (calf production and survival) influences population performance. The moose (Alces alces) population in northeastern Minnesota, USA, has declined 65% from 2006 to 2018 but has begun to stabilize. Because causes of this decline were largely unknown, we investigated production, survival, and cause-specific mortality of calves of the global positioning system (GPS)-collared females in this population. In 2013 and 2014, we GPS-collared 74 neonates and monitored them for survival. In 2015 and 2016, we monitored 50 and 35 calving females for signs of neonatal mortality using changes in adult female velocities and assessed seasonal calf survival by aerial surveys. In 2013 and 2014 (pooled), survival to 9 months was 0.34 (95% CI = 0.23–0.52) for collared calves, and in 2015 and 2016 (pooled) survival was 0.35 (95% CI = 0.26–0.48) for uncollared calves. Mortality in all 4 years was high during the first 50 days of life. In 2013 and 2014 (pooled), calving sites were relatively safe for collared neonates; predator-kills occurred a median 17.0 days after departure and a median 1,142 m from calving sites. Predation was the leading cause of death of collared calves (84% of mortalities), with wolves (Canis lupus) accounting for 77% of these. Other forms of mortality for collared and uncollared calves included drowning, infection, vehicle collision, and natural abandonment. We documented higher wolf predation than other recent studies with similar predator communities. Identifying specific causes of calf mortality and understanding their relations to various landscape characteristics and other extrinsic factors should yield insight into mechanisms contributing to the declining moose population in northeastern Minnesota and serve as a basis for ecologically sound management responses. © 2019 The Wildlife Society.     

Relative costs of offspring sex and offspring survival in a polygynous mammal

Costs of reproduction are expected to be ubiquitous in wild animal populations and understanding the drivers of variation in these costs is an important aspect of life-history evolution theory. We use a 43 year dataset from a wild population of red deer to examine the relative importance of two factors that influence the costs of reproduction to mothers, and to test whether these costs vary with changing ecological conditions. Like previous studies, our analyses indicate fitness costs of lactation: mothers whose calves survived the summer subsequently showed lower survival and fecundity than those whose calves died soon after birth, accounting for 5% and 14% of the variation in mothers'' survival and fecundity, respectively. The production of a male calf depressed maternal survival and fecundity more than production of a female, but accounted for less than 1% of the variation in either fitness component. There was no evidence for any change in the effect of calf survival or sex with increasing population density.     

Effects of predator treatments,individual traits,and environment on moose survival in Alaska

We studied moose (Alces alces) survival, physical condition, and abundance in a 3-predator system in western Interior Alaska, USA, during 2001–2007. Our objective was to quantify the effects of predator treatments on moose population dynamics by investigating changes in survival while evaluating the contribution of potentially confounding covariates. In May 2003 and 2004, we reduced black bear (Ursus americanus) and brown bear (U. arctos) numbers by translocating bears ≥240 km from the study area. Aircraft-assisted take reduced wolf (Canis lupus) numbers markedly in the study area during 2004–2007. We estimated black bears were reduced by approximately 96% by June 2004 and recovered to within 27% of untreated numbers by May 2007. Brown bears were reduced approximately 50% by June 2004. Late-winter wolf numbers were reduced by 75% by 2005 and likely remained at these levels through 2007. In addition to predator treatments, moose hunting closures during 2004–2007 reduced harvests of male moose by 60% in the study area. Predator treatments resulted in increased calf survival rates during summer (primarily from reduced black bear predation) and autumn (primarily from reduced wolf predation). Predator treatments had little influence on survival of moose calves during winter; instead, calf survival was influenced by snow depth and possibly temperature. Increased survival of moose calves during summer and autumn combined with relatively constant winter survival in most years led to a corresponding increase in annual survival of calves following predator treatments. Nonpredation mortalities of calves increased following predator treatments; however, this increase provided little compensation to the decrease in predation mortalities resulting from treatments. Thus, predator-induced calf mortality was primarily additive. Summer survival of moose calves was positively related to calf mass (β > 0.07, SE = 0.073) during treated years and lower (β = −0.82, SE = 0.247) for twins than singletons during all years. Following predator treatments, survival of yearling moose increased 8.7% for females and 21.4% for males during summer and 2.2% for females and 15.6% for males during autumn. Annual survival of adult (≥2 yr old) female moose also increased in treated years and was negatively (β = −0.21, SE = 0.078) related to age. Moose density increased 45%, from 0.38 moose/km² in 2001 to 0.55 moose/km² in 2007, which resulted from annual increases in overall survival of moose, not increases in reproductive rates. Indices of nutritional status remained constant throughout our study despite increased moose density. This information can be used by wildlife managers and policymakers to better understand the outcomes of predator treatments in Alaska and similar environments. © 2011 The Wildlife Society.     

Estimated calf and perinatal mortality in western North Atlantic right whales (Eubalaena glacialis)

Reduced reproductive success has contributed to lack of recovery of the endangered western North Atlantic right whale (Eubalaena glacialis). Here we examined the specific life history period from just before birth through the first year to estimate calf and perinatal losses between 1989 and 2003. The lower bound estimate (17 mortalities from 208 calving events) included documented calf mortalities and presumed deaths from serious injury or disappearance from the sighting record. The upper bound estimated potential calf losses from females with delayed first parturition (>10 yr) and shortened (2 yr) or lengthened (≥4 yr) calving intervals, if the female migrated to the calving ground during these intervals. Because cows were sighted in the calving ground predominantly in years when they were available to calve, adult females sighted there in a possible calving year without a calf were assumed to have experienced a perinatal loss. Twenty-eight potential perinatal losses were detected, bringing the upper bound of calf and perinatal mortality to 45 (3.0 calves/yr). The high frequency of lengthened calving intervals in E. glacialis suggests that abortion and neonatal losses are contributing to lower reproductive success compared to Southern Hemisphere right whales (Eubalaena australis).     

THE LIFE HISTORY OF FREE-RANGING ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS): AGE CLASSES, COLOR PHASES, AND FEMALE REPRODUCTION

Atlantic spotted dolphins (Stenella frontalis) were observed underwater and from the surface from 1985 to 1996 and photographed through successive years. Individuals were categorized into age classes by their degree of spotting and color phases. Dolphins spent an average of 3 yr in the two-tone color phase, 5 yr in the speckled phase, 7 yr in the mottled phase and up to 10 yr or more in the fused phase.
Sex ratios were close to parity, with old adults skewed towards females and juveniles and young adults skewed towards males. The average calving interval for 24 females was 2.96 years with a range of 1–5 yr. Females whose calves survived the first year had a significantly longer calving interval (3.56 years). The ages of first parturition for five females were estimated to be 10–12 yr. The age at sexual maturation was estimated to range from 8 to 15 yr.
Pregnancy rate fluctuated annually, with an average rate of 0.25 (range 0.07–0.57). Annual average birth rate was 0.08 (range 0.07–0.14), average calf production was 0.33 (range 0.06–0.52), average fecundity was 0.23 (range 0.13–0.30), and average recruitment was 0.06 (range 0.03–0.08). Most females who lost a calf conceived the same or following year.
Lactation lasted up to 5 yr, and 45% of visibly pregnant females were also lactating. Age of first parturition was associated with the mottled color phase. Average first-year mortality rate of calves was 0.24.     

Calving rate,calf survival rate,and habitat selection of forest-dwelling caribou in a highly managed landscape

Logging negatively affects the threatened forest-dwelling caribou (Rangifer tarandus caribou) through its positive effects on large predator populations. As recruitment is a key component of caribou population growth rate, we assessed calving rates of females and calf survival rates during the most critical period for calf survival, the calving period. We also identified causes of calf mortality and investigated the influence of predation risk, food availability, and human disturbance on habitat selection of females during the calving period at both the home-range and forest stand scales. We hypothesized that caribou should display habitat selection patterns to reduce predation risk at both scales. Using telemetry, we followed 22 females and their calves from 2004 to 2007 in a highly managed study area in Québec, Canada. Most females (78.5 ± 0.05 [SE]) gave birth each year, but only 46.3 ± 8.0% of the calves survived during the first 50 days following birth, and 57.3 ± 14.9% of them died from black bear (Ursus americanus) predation. At the home-range scale, caribou selected calving areas located at upper slope positions and avoided high road density areas. Surprisingly, they also selected the forested habitat type having the lowest lateral cover (mixed and deciduous stands) while avoiding the highest cover (regenerating conifer stands). At the forest stand scale, caribou selected areas located at relatively high elevations and with a lower basal area of black spruce trees. The selection of upper slope positions likely favored spatial segregation between calving females and wolves (Canis lupus) but not black bear. Our results suggest that calving females used areas from which they could visually detect approaching predators. While wolf avoidance appeared to be effective in a highly managed landscape, caribou did not appear to have adjusted their predator avoidance strategy to the recent increase in black bear abundance, who have benefited from increased food abundance. This situation requires focused attention from wildlife managers as logging activities are progressing towards the north within the core of forest-dwelling caribou range. © 2011 The Wildlife Society.     

Influence of Predator Harvest,Biological Factors,and Landscape on Elk Calf Survival in Idaho

ABSTRACT We evaluated survival of elk (Cervus elaphus) calves on 2 contrasting study areas in north-central Idaho, USA, from 1997 to 2004. Recruitment was modest (>30 calves:100 F [calves of either sex: F elk 1 yr old]) and stable on the South Fork study area and low (<20 calves:100 F) and declining on the Lochsa study area. The primary proximate cause of calf mortality on both study areas was predation by black bears (Ursus americanus) and mountain lions (Puma concolor). We experimentally manipulated populations of black bears and mountain lions on a portion of each study area. Black bear harvest (harvest density/600km²) initially doubled on the Lochsa treatment after manipulating season bag limits. Mountain lion harvest also increased by 60% but varied widely during the manipulation period. Harvest seasons were closed for black bears and mountain lions on the treatment portion of the South Fork study area. Using the Andersen—Gill formulation (A-G) of the Cox proportional hazards model, we examined effects of landscape structure, predator harvest levels, and biological factors on summer calf survival. We used Akaike's Information Criterion (AIC_c) and multimodel inference to assess some potentially useful predictive factors relative to calf survival. We generated risk ratios for both the best models and for model-averaged coefficients. Our models predicted that calf survival was influenced by biological factors, landscape surrounding calf locations, and predator harvest levels. The model that best explained mortality risk to calves on the Lochsa included black bear harvest (harvest density/600 km²), estimated birth mass of calves, and percentage of shrub cover surrounding calf locations. Incorporating a shrub X time interaction allowed us to correct for nonproportionality and detect that effect of shrub cover was only influential during the first 14 days of a calf's life. Model-averaging indicated that estimated birth mass of calves and black bear harvest were twice as important as the next variables, but age of calves at capture was also influential in calf survival. The model that best explained mortality risk to calves on the South Fork included black bear harvest, age of calves at capture, and gender of calves. Model-averaging indicated that age at capture and black bear harvest were twice as important as the next variable, forest with 33–66% canopy cover (Canopy 33–66). Risk to calves decreased when calves occupied areas with more of this forest cover type. Model-averaging also indicated that increased mountain lion harvest lowered calf mortality risk 4% for every 1-unit increase in lion harvest (harvest density/600 km²) but was lower (<25%) in importance compared to age at capture and black bear harvest. Our results suggest that levels of predator harvest, and presumably predator density, resource limitations expressed through calf birth mass, and habitat structure had substantial effects on calf survival. Our results can be generalized to other areas where managers are dealing with low calf elk recruitment. However, because factors vary spatially, a single management strategy applied in different areas will probably not have the same effect on calf survival.     

REPRODUCTION IN FEMALE MANATEES OBSERVED IN SARASOTA BAY, FLORIDA

Resightings of recognizable individual Florida manatees, Trichechus manatus latirostris , in Sarasota Bay provided information on life history and reproductive parameters. These parameters have been documented at winter aggregation sites, but few data existed for Florida's west coast at non-winter sites. Life history data are needed to estimate annual reproduction and survival rates and construct population models for manatees along west central Florida. Observations of 113 recognizable manatees of known sex sighted between 1993 and 1997 indicated a 1: 1 sex ratio. Fifty-three females produced at least 55 calves during five years of observation. Two large, presumably sexually mature females were never observed with calves in over five years of monitoring. Not surprisingly, several reproductive parameters matched those measured in previous studies at winter sites with a mean of 1.8 seasons of calf dependence, 2.2 seasons between births, and age of sexual maturity at 3–4 yr. Birth rates, fecundity, and proportions of females with calves varied only slightly among investigations.     

Maternal Behavior Indicates Survival and Cause-Specific Mortality of Moose Calves

Continuing research on cause-specific mortality and annual survival of moose (Alces alces) calves in northeastern Minnesota, USA, is important to understanding the long-term trajectory of the population. In 2013 and 2014, we observed global positioning system (GPS)-collared, female moose exhibit a specific behavior (i.e., mortality movement) associated with the death of their GPS-collared neonate. The females made a rapid, long-distance movement (flee), followed by a return to the calf mortality site. We used characteristics of this movement in 2013–2014 (n = 46) to develop models for assessing calf survival, and then evaluated these models using female movement rates (n = 49) in 2015−2016. Using this behavior as an indicator of calf mortality in 2016, we conducted field investigations, leading to evidence of 15 mortalities at a mean age of 30.6 ± 15.5 (SE) days (range = 3–243 days). We launched 21 investigations in response to a mortality movement and they resulted in confirmation of 11 of the 15 calf mortalities. Specific causes of mortality included 9 wolf (Canis lupus)-kills, 3 black bear (Ursus americanus)-kills, 1 unknown predator-kill, and 2 deaths following vehicle collisions. The mean distance females fled after a mortality was 1,873 ± 412 m (range = 126–5,805 m, n = 14). Females that made return visits returned a mean 2.8 ± 0.5 times (range = 1–5, n = 8) to within a mean 106 ± 22 m (range = 34–230 m, n = 8) of the mortality site. Calf survival to 30 days of age was 67 ± 8% (95% CI = 53–84%, n = 36) but declined to 53 ± 8% (95% CI = 39–72%, n = 36) by 3 months of age. We developed 2 population-level movement models to improve the efficacy of using the mortality movement to identify and locate calf mortalities in real time via field investigations. The first approach, a temporal-based model, used a 3-day average movement velocity threshold (118 m/hr) for all females to indicate calf mortality and accurately predicted survival status in 51% (n = 105) of the cases. The second approach, an age-specific model using different thresholds (28–135 m/hr) for females relative to calf age, was 80% (n = 231) accurate. Using movement behavior of females to assess calf mortality yielded important insights into mechanisms influencing the population decline that will inform future management decisions. © 2019 The Wildlife Society     

Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Predation is a major limiting factor for most small sedentary caribou (Rangifer tarandus) populations, particularly those that are threatened or endangered across the southern extent of the species’ range. Thus, reducing predation impacts is often a management goal for improving the status of small caribou populations, and lethal predator removal is the primary approach that has been applied. Given that predator control programs are often contentious, other management options that can garner broader public acceptance need to be considered. Substantial calf losses to predation in the few weeks following birth are common for these small caribou populations. Therefore, we employed a novel experimental approach of maternal penning with the goal of reducing early calf mortality in the Chisana Caribou Herd, a declining population in southwest Yukon and adjacent Alaska thought to number around 300 individuals. Maternal penning entailed temporarily holding pregnant females on their native range in a large pen secure from predators from late March through the initial weeks of calf rearing to mid-June. During 2003–2006, we conducted 4 annual penning trials with 17–50 pregnant females each year (n = 146 total), assessed survival of calves born in the pens, and evaluated survival and nutritional effects of penning for females that were held. We also investigated the herd's population dynamics during 2003–2008 to determine effects of maternal penning on calf recruitment and population growth. In addition to information gained during maternal penning, we determined natality and survival patterns via radiotelemetry, conducted autumn age-sex composition surveys each year, and censused the population in mid-October 2003, 2005, and 2007. Based on our penning trials and demographic investigations, we used simulation models to evaluate the effects of maternal penning relative to a population's inherent growth rate (finite rate of increase [λ] without maternal penning) and penning effort (proportion of calves born in penning) to provide perspective on utility of this approach for improving the status of small imperiled caribou populations. Pregnant females held in maternal penning tolerated captivity well in that they exhibited positive nutritional responses to ad libitum feed we provided and higher survival than free-ranging females (0.993 and 0.951 for penned and free-ranging females, respectively). Survival of pen calves from birth to mid-June was substantially higher than that of free-ranging calves ( = 0.950 and 0.376, respectively). This initial period accounted for 76% of the annual calf mortality in the free-ranging population. Pen-born calves maintained their survival advantage over wild-born calves to the end of their first year ( = 0.575 and 0.192, respectively) during years penning occurred. Females in the Chisana Herd were highly productive with 57% producing their first offspring at 2 years of age, and annual natality rates averaging 0.842 calves/female ≥2 years old. Age-specific natality rates exceeded 0.900 for 4–9-year-olds, then exhibited senescent decline to 0.467 by 19 years old. Annual survival of free-ranging adult females and calves averaged 0.892 and 0.184, respectively, over all study years; both were reduced during 2004 because of poor winter survival. We noted reduced nutritional condition of caribou late that winter in that females we captured were lighter than in other years and produced lighter calves. We suspect that the reduced survival during winter 2004 and the observed nutritional characteristics resulted from adverse snow conditions in combination with effects of the extreme drought experienced the previous summer. Age-specific survival of adult females was ≥0.900 through 10 years of age, then declined with age. The Chisana Herd numbered 720 caribou in mid-October 2003, or more than twice that estimated prior to initiating maternal penning, and increased to 766 caribou by mid-October 2007. We calculated that penning added 54.2 yearling recruits, or 40% of calves released from penning. Based on the maternal penning results and the population's vital rates, we determined that the herd would have been stable during 2003–2007 at about 713 caribou without maternal penning; thus, the increase in herd size we observed resulted from maternal penning and was equivalent to the estimate of additional yearling recruits. The improvement in the population trend invoked by maternal penning was limited by the larger than expected population size and resulting low penning effort ( = 11% of calves born in pen). Our simulations corroborated that maternal penning increased population size by the number of additional recruits provided, even at low penning effort, for inherently stable populations. As the inherent rate of increase dropped below λ = 1.000, more of the additional recruits from penning were needed to offset the downward population inertia, thus requiring increased penning effort to reach stability. For populations declining at λ < 0.890, stability could not be achieved with 100% penning effort given the vital rates in our models. Maternal penning in its limited application to date has proven to be broadly popular as a nonlethal management action aimed at reducing initial calf mortality from predation in small caribou populations. However, based on the Chisana program and 3 subsequent efforts elsewhere, improvement in population trends have been modest at best and come at a high financial cost. Given the necessity of maximizing penning effort, maternal penning may have a role in addressing conservation challenges for some small caribou populations that are stable or slowly declining, but its application should be primarily driven by objective assessment of the likelihood of improving population trends rather than popularity relative to other management options.     

Causes and correlates of calf mortality in captive Asian elephants (Elephas maximus)

Juvenile mortality is a key factor influencing population growth rate in density-independent, predation-free, well-managed captive populations. Currently at least a quarter of all Asian elephants live in captivity, but both the wild and captive populations are unsustainable with the present fertility and calf mortality rates. Despite the need for detailed data on calf mortality to manage effectively populations and to minimize the need for capture from the wild, very little is known of the causes and correlates of calf mortality in Asian elephants. Here we use the world''s largest multigenerational demographic dataset on a semi-captive population of Asian elephants compiled from timber camps in Myanmar to investigate the survival of calves (n = 1020) to age five born to captive-born mothers (n = 391) between 1960 and 1999. Mortality risk varied significantly across different ages and was higher for males at any age. Maternal reproductive history was associated with large differences in both stillbirth and liveborn mortality risk: first-time mothers had a higher risk of calf loss as did mothers producing another calf soon (<3.7 years) after a previous birth, and when giving birth at older age. Stillbirth (4%) and pre-weaning mortality (25.6%) were considerably lower than those reported for zoo elephants and used in published population viability analyses. A large proportion of deaths were caused by accidents and lack of maternal milk/calf weakness which both might be partly preventable by supplementary feeding of mothers and calves and work reduction of high-risk mothers. Our results on Myanmar timber elephants with an extensive keeping system provide an important comparison to compromised survivorship reported in zoo elephants. They have implications for improving captive working elephant management systems in range countries and for refining population viability analyses with realistic parameter values in order to predict future population size of the Asian elephant.     

Life history plasticity and population regulation in sea otters

We contrasted body condition, and age‐specific reproduction and mortality between a growing population of sea otters (Enhydralutris) at Kodiak Island and a high‐density near‐equilibrium population at Amchitka Island, Alaska. We obtained data from marked individuals, population surveys, and collections of beach‐cast carcasses. Mass:length ratios indicated that females (but not males) captured in 1992 at Amchitka were in poorer condition than those captured at Kodiak in 1986–1987. In 1993, the condition of females at Amchitka improved in apparent response to two factors: (1) an episodic influx of Pacific smooth lumpsuckers, Aptocyclus ventricocus, from the epi‐pelagic zone, which otters consumed; and (2) an increase in the otters’ benthic invertebrate prey resulting from declining otter numbers. Reproductive rates varied with age (0.37 [CI=0.21 to 0.53] births female^?1 yr^?1 for 2–3‐yr‐olds, and 0.83 [CI=0.69 to 0.90] for females ≥4 yr old), and were similar at both areas. Weaning success (pups surviving to ≥120 d), in contrast, was almost 50% lower at Amchitka than at Kodiak and for females ≥4 yr of age was 0.52 (CI=0.38 to 0.66) vs 0.94 (CI=0.75 to 0.99), respectively. Sixty‐two percent of the preweaning pup losses at Amchitka occurred within a month of parturition and 79% within two months. Postweaning survival was also low at Amchitka as only 18% of instrumented pups were known to be alive one year after mother‐pup separation. Adult survival rates appeared similar at Amchitka and Kodiak. Factors affecting survival early in life thus are a primary demographic mechanism of population regulation in sea otters. By maintaining uniformly high reproductive rates over time and limiting investment in any particular reproductive event, sea otters can take advantage of unpredictable environmental changes favorable to pup survival. This strategy is consistent with predictions of “bet‐hedging” life history models.     

Reproduction in wild female olive baboons

The purpose of this paper is to evaluate several factors that influence female reproduction in a large troop of wild olive baboons (Papio cynocephalus anubis) based on 4 consecutive years of demographic data. Interbirth intervals were significantly shorter for females whose infants died before their next conception than for females whose infants survived. High-ranking mothers of surviving infants had significantly shorter birth intervals than comparable low-ranking mothers, independent of maternal age. This occurred mainly because the interval from resumption of cycling to conception was significantly shorter for high-vs. low-ranking females. Dominance rank did not influence sex ratio at birth, infant survival in the first 2 years, or adult female mortality. Age was also significantly related to interbirth intervals, with older females having shorter intervals. Primiparous females had consistently longer reproductive intervals than did multiparous females, but this difference reached statistical significance only for females whose infants died before the next conception. Primiparous females also experienced significantly higher infant mortality. Data on body size and estrous cycle length indicated no differences between high- and low-ranking females. Nutritional and stress-related mechanisms that may underlie the reproductive advantages of high rank are discussed.     

Life history of the Indo‐Pacific humpback dolphin in the Pearl River Estuary,southern China

We studied life history characteristics of the Hong Kong/Pearl River Estuary population of Indo‐Pacific humpback dolphins (Sousa chinensis), based on data from 120 specimens stranded between 1995 and 2009, 40 individuals biopsied at sea, and a long‐term (14+ yr) photo‐identification study. Ages were determined for 112 specimens by thin‐sectioning teeth and counting growth layer groups. Estimated length at birth was 101 cm. Longevity was at least 38 yr, and there was little difference in growth patterns of males and females. Growth was described by a Bayesian two‐phase Gompertz model; asymptotic length was reached at 249 cm. The tooth pulp cavity filled at an average of 18.5 yr of age. Physical maturity was reached at between 14 and 17 yr of age, apparently a few years after attainment of sexual maturity. Maximum lengths and weights of about 268 cm and 240 kg were attained. Females appear to lose all their spots by 30 yr, although males may retain some spotting throughout life. Calving occurred throughout the year, with a broad peak from March to June. Of 60 females monitored at sea for >14 yr of the study, none were documented to have more than three calves, suggestive of low reproductive output or low calf survival.     

Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont,USA

Moose (Alces alces) have experienced considerable declines along the periphery of their range in the northeastern United States. In Vermont, the population declined 45% from 2010 to 2017 despite minimal hunter harvest and adequate habitat. Similarly, nearby populations recently experienced epizootics characterized by >50% mortality. Declines have largely been associated with the effects of winter ticks (Dermacentor albipictus), but uncertainty exists about the effects of environmental and other parasite-related conditions on moose survival. We examined patterns of moose survival among a radio-collared population (n = 127) in Vermont from 2017 to 2019. Our objectives were to estimate causes of mortality and model survival probability as a function of individual and landscape variables for calves (<1 yr) and adults (≥1 yr). Observed adult survival was 90% in 2017, 84% in 2018, and 86% in 2019, and winter calf survival was 60% in 2017, 50% in 2018, and 37% in 2019. Winter tick infestation was the primary cause of mortality (91% of calves, 25% of adults), and 32% of all mortalities had evidence of meningeal worm (Parelaphostrongylus tenuis). Other sources of mortality such as vehicles, harvest, predation, deep snow, and other parasitic infections were negligible. The best supported calf model included sex differences and negative effects of tick engorgement (%/week) and parasite level (roundworm and lungworm). The best supported adult model included the effect of cumulative tick engorgement (cumulative %/week), which negatively affected survival. Our results indicate that winter tick engorgement strongly affects survival, and is probably compounded by the presence of meningeal worm and other parasites. Reduced tick effects may be achieved by decreasing moose density through harvest and managing late winter habitat to minimize tick density. Management of white-tailed deer (Odocoileus virginianus) density may also affect the transmission of meningeal worm. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Induced orphaning reveals post-weaning maternal care in reindeer

A common by-product of human harvesting is orphaning of calves in autumn. Despite this, there are few studies in northern and temperate ungulates evaluating the fate of orphaned calves and the potential benefits to offspring and costs to mothers of post-weaning maternal care. We manipulated orphaning and forage distribution during winter for two herds of reindeer (Rangifer tarandus): one nonfed and the other supplementally fed to increase level of interference competition. Both herds consisted of females with and without calves at heel and orphaned calves. We measured survival and somatic losses during winter and distances between mother–calves and adult females–orphans within the herds. All females survived the winter, and there was no evidence of post-weaning maternal cost in terms of female’s mass loss. The winter mortality among calves was negligible and did not differ between orphans as compared to nonorphans. However, nonorphaned calves lost less mass and stayed closer to their mothers than orphans to adult females, suggesting that increased mortality might occur in harsher winters. This tended to be more marked in the fed group where interference competition was more likely due to feed being concentrated both in space and time. Reduced mass loss in nonorphans is therefore most likely due to mothers sharing and defending feeding resources and protecting their offspring from harassment by other herd members during their first winter. We conclude that hunting practise of northern and temperate ungulates where females having calf/calves at heel are intentionally or non-intentionally harvested, may have demographic side effects at least in harsh winters.     

Summer elk calf survival in a partially migratory population

Decomposing variation in juvenile recruitment is a key component of understanding population dynamics for partially migratory ungulates. We investigated reproductive parameters of adult female elk (Cervus canadensis) with calves at heel, and survivorship, cause-specific mortality, and intrinsic and extrinsic factors affecting risk of mortality for calves in a partially migratory elk population from 2013–2016 in Alberta, Canada. Elk calves born to resident mothers had 45% lower survivorship on average compared to migrant calves (0.24 vs. 0.69) and nearly twice the mortality rate (0.37 vs. 0.19) from bears (Ursus spp.), the dominant source of mortality. Contrary to our predictions, we found that increasing levels of maternal ingesta-free body fat were associated with increasing risk of calf mortality, indicating predation may have overwhelmed nutritional effects. We found no evidence that timing of calf birth or birth weight differed between migratory tactics or influenced mortality risk. We found that as percentage of cut forest increased, risk of calf mortality marginally decreased, which benefited migrant elk that were exposed to more clear-cuts compared to residents. Exposure to bear predation risk was unimportant during the hiding phase (≤10 days after birth) for either migratory tactic, presumably because neonatal hiding behavior reduced vulnerability. In contrast, bear predation risk was important for mortality risk after 10 days in age, especially for resident elk calves, which were exposed to higher bear predation risk compared to migrants. We conclude that relative differences in bear predation between migratory tactics are contributing to the dynamics of partial migration in this population through additive effects on calf mortality. Thus, wildlife managers should anticipate that recovering grizzly bear (U. arctos) populations may substantially lower elk recruitment through effects on summer calf survival, especially in areas with diverse carnivore assemblages.     

PHYSIOLOGICAL AND BEHAVIORAL DEVELOPMENT IN DELPHINID CALVES: IMPLICATIONS FOR CALF SEPARATION AND MORTALITY DUE TO TUNA PURSE-SEINE SETS

Tuna purse-seiners in the eastern tropical Pacific (ETP) capture yellowfin tuna by chasing and encircling herds of associated dolphins. This fishery has caused mortality in 14 dolphin species (20 stocks) and has led to significant depletions of at least three stocks. Although observed dolphin mortality is currently low, set frequency remains high and dolphin stocks are not recovering at expected rates. Mortality of nursing calves permanently separated from their mothers during fishery operations may be an important factor in the lack of population recovery, based on the recent discovery that calves do not accompany 75%–95% of lactating females killed in the purse-seine nets. We assessed age-specific potential for mother–calf separations and subsequent mortality of calves by reviewing and synthesizing published data on physiological and behavioral development in delphinids from birth through 3 yr postpartum. Results indicate that evasive behavior of mothers, coupled with the developmental state of calves, provides a plausible mechanism for set-related mother–calf separations and subsequent mortality of calves. Potential for set-related separation and subsequent mortality is highest for 0–12-mo-old dolphins and becomes progressively lower with age as immature dolphins approach adult stamina and attain independence.     

Living on the Edge: Viability of Moose in Northeastern Minnesota

ABSTRACT North temperate species on the southern edge of their distribution are especially at risk to climate-induced changes. One such species is the moose (Alces alces), whose continental United States distribution is restricted to northern states or northern portions of the Rocky Mountain cordillera. We used a series of matrix models to evaluate the demographic implications of estimated survival and reproduction schedules for a moose population in northeastern Minnesota, USA, between 2002 and 2008. We used data from a telemetry study to calculate adult survival rates and estimated calf survival and fertility of adult females by using results of helicopter surveys. Estimated age- and year-specific survival rates showed a sinusoidal temporal pattern during our study and were lower for younger and old-aged animals. Estimates of annual adult survival (when assumed to be constant for ages >1.7 yr old) ranged from 0.74 to 0.85. Annual calf survival averaged 0.40, and the annual ratio of calves born to radiocollared females averaged 0.78. Point estimates for the finite rate of increase (λ) from yearly matrices ranged from 0.67 to 0.98 during our 6-year study, indicative of a long-term declining population. Assuming each matrix to be equally likely to occur in the future, we estimated a long-term stochastic growth rate of 0.85. Even if heat stress is not responsible for current levels of survival, continuation of this growth rate will ultimately result in a northward shift of the southern edge of moose distribution. Population growth rate, and its uncertainty, was most sensitive to changes in estimated adult survival rates. The relative importance of adult survival to population viability has important implications for harvest of large herbivores and the collection of information on wildlife fertility.     

Occurrence of neonatal and postnatal mortality in range beef cattle. I. Calf loss incidence from birth to weaning, backward and breech presentations and effects of calf loss on subsequent pregnancy rate of dams

Data from 13,296 calvings collected over a 15-yr period indicated 893 calves died from birth to weaning for an average loss of 6.7%. Calves lost from birth through Day 3 postcalving accounted for a 4.6% loss with an additional 2.1% loss from Day 4 through weaning. Calf deaths from primiparous 2- and 3-yr-old dams accounted for 41.0% of total mortality. Losses within groups were primiparous 2-yr-olds, 10.9%; primiparous 3-yr-olds, 8.7%; second-calf 3-yr-olds, 4.1%; second-calf 4-yr-olds, 8.3%; multiparous 4-yr-olds, 4.8%; and dams 5 yr and older, 5.3%. The majority of calf deaths (57.4%) occurred within the first 24 h postpartum with 75% of the total occurring Days 0 through 7. This loss was similar among all dam age and parity groups. Calf death due to dystocia accounted for the single largest loss category through the first 96 h postpartum, resulting in 69.6, 39.6, 30.8 and 33.3% of the loss incidence for Day 0, 1, 2 and 3 postpartum, respectively. More (P < 0.01) male calves (510, 57.6%) died than females (376, 42.4%). Backward presentations occurred more frequently (P < 0.01) than breech (1.6 vs 0.6% of all births, respectively). Incidence of backward presentation was 2.3%, 5.6% and 0.9% for primiparous 2-yr-old, 3-yr-old and multiparous dams, respectively (P < 0.01); 64.2% of the backward calves were males and 35.8% females (P < 0.01). Survival of calves in backward presentation exceeded (P < 0.01) that of breech calves (70.7 vs 32.9%). Fall pregnancy rate of dams that lost calves and reentered the breeding herd that same year was 72.4% compared to 79.4% (P < 0.01) for contemporary females that did not lose calves. The depression in pregnancy rate was not specifically due to dystocia but apparently to some general effect of calf loss.