共查询到20条相似文献，搜索用时 15 毫秒
1.
William. D. Bowen Cornelia E. den Heyer Jim I. McMillan Sara J. Iverson 《Ecology and evolution》2015,5(7):1412-1424
Offspring size affects survival and subsequent reproduction in many organisms. However, studies of offspring size in large mammals are often limited to effects on juveniles because of the difficulty of following individuals to maturity. We used data from a long‐term study of individually marked gray seals (Halichoerus grypus; Fabricius, 1791) to test the hypothesis that larger offspring have higher survival to recruitment and are larger and more successful primiparous mothers than smaller offspring. Between 1998 and 2002, 1182 newly weaned female pups were branded with unique permanent marks on Sable Island, Canada. Each year through 2012, all branded females returning to the breeding colony were identified in weekly censuses and a subset were captured and measured. Females that survived were significantly longer offspring than those not sighted, indicating size‐selective mortality between weaning and recruitment. The probability of female survival to recruitment varied among cohorts and increased nonlinearly with body mass at weaning. Beyond 51.5 kg (mean population weaning mass) weaning mass did not influence the probability of survival. The probability of female survival to recruitment increased monotonically with body length at weaning. Body length at primiparity was positively related to her body length and mass at weaning. Three‐day postpartum mass (proxy for birth mass) of firstborn pups was also positively related to body length of females when they were weaned. However, females that were longer or heavier when they were weaned did not wean heavier firstborn offspring. 相似文献
2.
We report on a method of visually classifying Pacific walruses (Odobenus rosmarus) to sex and age class with the goal of estimating calf:cow ratios. Development of this method began in 1958 by Dr. F. H. Fay and was used during six surveys in the Chukchi Sea between 1981 and 1999. We estimate calf:cow ratios using beta‐binomial models to allow for overdispersion and use Monte Carlo simulations to assess the reliability of prior surveys and quantify sample sizes required for future surveys. Calf:cow ratios did not vary by region, date, or by the number of cows in a group. However, higher ratios were observed in the morning and evening than during the day, indicating haul out behavior of cows varies by reproductive status. Adjusted for solar noon, few calves were observed in 1981 (3:100), 1984 (6:100), and 1998 (5:100), while substantially more were observed in 1982 (15:100) and 1999 (13:100). Classifying between 200 and 300 groups with cows (~1,600–2,300 individual cows) will yield calf:cow ratios with ~20%–30% relative precision. Tagging studies that examine hauling‐out behavior of cows with and without calves relative to time‐of‐day are necessary to better understand how to interpret calf:cow ratios. 相似文献
3.
Abstract: The paper describes the use of the drugs Zoletil® and etorphine for the immobilization of walrus ( Odobenus rosmarus rosmarus ) for attachment of satellite telemetry equipment. Three animals weighing approximately 1,500 kg each were injected intramuscularly with Zoletil® at a dose between 1.4 and 2.2 mg/kg. One walrus died while the two others were adequately restrained. The induction time was between 14 and 29 minutes and the effect lasted for 75-220 min.
Thirty-eight animals of weight 900-1,500 kg were darted intramuscularly with etorphine at a dose between 3.3 and 8 mg/kg. Thirty-six were immobilized although one died later. The induction time for etorphine was two to ten minutes. The action of this drug was terminated with an injection of the antidote di-prenorphine.
The use of etorphine was accompanied by convulsive movements and apnoea while Zoletil® produced a gradual and smooth entry into and withdrawal from immobilization. 相似文献
Thirty-eight animals of weight 900-1,500 kg were darted intramuscularly with etorphine at a dose between 3.3 and 8 mg/kg. Thirty-six were immobilized although one died later. The induction time for etorphine was two to ten minutes. The action of this drug was terminated with an injection of the antidote di-prenorphine.
The use of etorphine was accompanied by convulsive movements and apnoea while Zoletil® produced a gradual and smooth entry into and withdrawal from immobilization. 相似文献
4.
Andrew D. Lowther Kit M. Kovacs David Griffiths Christian Lydersen 《Marine Mammal Science》2015,31(4):1291-1313
Motivational changes in animals are likely to be detectable retrospectively through observed changes in behavior. Breeding represents one of the strongest motivational states in mammals, and its timing is often tied to a seasonally optimal suite of environmental and physical conditions. While seasonal changes in behavior may be directly observable in some species, for others that breed cryptically or in difficult to access areas, detecting behavioral changes may only be feasible using data collected remotely. Herein, we explore whether behavioral changes can be used to infer motivational state for a wild, free‐ and wide‐ranging high arctic marine mammal, adult male Atlantic walruses (Odobenus rosmarus rosmarus). Using satellite‐relayed location and dive data from 23 adult male walruses instrumented in the Svalbard Archipelago, we identify seasonal movement to discrete geographic regions deep into winter pack ice. Adult male walrus diving behavior underwent marked seasonal movements between geographical areas that coincided with changes in light regime. At offshore wintering sites adult males (n = 4) shifted from a summer pattern of deep, long benthic dives to much shallower diving. Some males performed similar shallow, winter dive behavior at coastal locations (n = 12) suggesting that breeding might also occur around the coast of Svalbard. However, interpretation of behavioral changes of these coastal individuals was challenging. The presumed breeding sites at the winter off‐shore locations were situated in areas where polynyas are known to occur, making them a predictable resource even if they are located deep inside the winter pack‐ice. We demonstrate that remotely collected behavioral data can be used to identify seasonally explicit changes in the behavior of cryptic species. 相似文献
5.
Individuals store energy to balance deficits in natural cycles; however, unnatural events can also lead to unbalanced energy budgets. Entanglement in fishing gear is one example of an unnatural but relatively common circumstance that imposes energetic demands of a similar order of magnitude and duration of life‐history events such as migration and pregnancy in large whales. We present two complementary bioenergetic approaches to estimate the energy associated with entanglement in North Atlantic right whales, and compare these estimates to the natural energetic life history of individual whales. Differences in measured blubber thicknesses and estimated blubber volumes between normal and entangled, emaciated whales indicate between 7.4 × 1010 J and 1.2 × 1011 J of energy are consumed during the course to death of a lethal entanglement. Increased thrust power requirements to overcome drag forces suggest that when entangled, whales require 3.95 × 109 to 4.08 × 1010 J more energy to swim. Individuals who died from their entanglements performed significantly more work (energy expenditure × time) than those that survived; entanglement duration is therefore critical in determining whales’ survival. Significant sublethal energetic impacts also occur, especially in reproductive females. Drag from fishing gear contributes up to 8% of the 4‐year female reproductive energy budget, delaying time of energetic equilibrium (to restore energy lost by a particular entanglement) for reproduction by months to years. In certain populations, chronic entanglement in fishing gear can be viewed as a costly unnatural life‐history stage, rather than a rare or short‐term incident. 相似文献
6.
State‐space models offer researchers an objective approach to modeling complex animal location data sets, and state‐space model behavior classifications are often assumed to have a link to animal behavior. In this study, we evaluated the behavioral classification accuracy of a Bayesian state‐space model in Pacific walruses using Argos satellite tags with sensors to detect animal behavior in real time. We fit a two‐state discrete‐time continuous‐space Bayesian state‐space model to data from 306 Pacific walruses tagged in the Chukchi Sea. We matched predicted locations and behaviors from the state‐space model (resident, transient behavior) to true animal behavior (foraging, swimming, hauled out) and evaluated classification accuracy with kappa statistics (κ) and root mean square error (RMSE). In addition, we compared biased random bridge utilization distributions generated with resident behavior locations to true foraging behavior locations to evaluate differences in space use patterns. Results indicated that the two‐state model fairly classified true animal behavior (0.06 ≤ κ ≤ 0.26, 0.49 ≤ RMSE ≤ 0.59). Kernel overlap metrics indicated utilization distributions generated with resident behavior locations were generally smaller than utilization distributions generated with true foraging behavior locations. Consequently, we encourage researchers to carefully examine parameters and priors associated with behaviors in state‐space models, and reconcile these parameters with the study species and its expected behaviors. 相似文献
7.
Lorrie D. Rea Brian S. Fadely Sean D. Farley Julie P. Avery Wendy S. Dunlap‐Harding Vicki K. Stegall Carrie A. B. Eischens Tom S. Gelatt Kenneth W. Pitcher 《Marine Mammal Science》2016,32(4):1200-1218
Steller sea lion (Eumetopias jubatus) young‐of‐the‐year (YOY) are nutritionally dependent upon their dam through the majority of their first year. Several indices of body condition were measured in YOY 1.5–9 mo of age captured in Southeast Alaska (n = 122), the Gulf of Alaska (n = 182), and the Aleutian Islands (n = 38) to test the hypothesis that nutritional stress impacted the ability of adult female Steller sea lions to adequately nourish their late gestation YOY in the central Aleutian Islands in the early 2000s. Body mass (kg) and percent total body lipid content (%TBL) increased with age in all three regions of Alaska that were sampled (P < 0.05). Young‐of‐the‐year 7–9 mo of age were leaner in Southeast Alaska (27.6% ± 1.0%) and Gulf of Alaska (29.5% ± 0.8%) than in the Aleutian Islands (35.7% ± 1.2%, P < 0.001). Condition indices calculated from morphometric measures did not strongly predict the %TBL measured by isotope dilution. The trend for Aleutian Island YOY to have larger body mass and larger body fat reserves are counter to what would be expected if dams were unable to adequately provision their late lactation YOY due to inadequate food availability in the central Aleutian Islands. 相似文献
8.
9.
Tiffany F. Keenan‐Bateman William A. McLellan Craig A. Harms Marina A. Piscitelli Susan G. Barco Victoria G. Thayer Gretchen N. Lovewell Karen L. Clark Paul K. Doshkov David S. Rotstein Charles W. Potter D. Ann Pabst 《Marine Mammal Science》2016,32(3):868-883
The parasitic nematode Crassicauda sp. was initially described in kogiid whales from specimens collected within cervical tissues, uncommon sites of infection for this parasite. Crassicauda sp. has only been reported in Kogia breviceps to date, but no study has yet investigated a large sample of both kogiid species. A 15 yr record of 104 kogiid strandings (K. sima, n = 40; K. breviceps, n = 64) in North Carolina and Virginia, U.S.A. was used to determine the prevalence of Crassicauda sp. across species, within species across sex, and within sex across length and life history categories. Crassicauda sp. was confirmed to be a species‐specific parasite among kogiids infecting only K. breviceps (prevalence = 45%). Within K. breviceps, prevalence was similar (45%) in both immature and mature males, but increased from 10% in immature to 76% in mature females. This study confirmed the cervico‐thoracic distribution of the parasite, and identified a novel site of infection in a previously undescribed exocrine gland associated with the pigmented “false gill slit.” The species‐specific nature of Crassicauda sp. infection, the exocrine gland, and the distinct features of the false gill slit pigmentation associated with the gland, are all useful characters to identify kogiid species in the field. 相似文献
10.
11.
Felipe Montalva Diego Prez‐Venegas Josefina Gutirrez Mauricio Seguel 《Ecology and evolution》2019,9(7):3689-3699
- Parasites are an important part of ecosystems, playing a critical role in their equilibrium. However, the consequences of parasitism beyond the direct effects associated with disease and mortality are not completely understood. This gap in knowledge is in part due to the difficulties to isolate the effect of single parasite species on physiological and behavioral traits in natural systems.
- The South American fur seal (Arctocephalus australis)–hookworm (Uncinaria sp.) interaction offers an ideal system to overcome these difficulties and study the behavioral and physiological effects of parasites in their hosts.
- Hookworms cause stunted growth and anemia in pinniped pups, which could affect early life active behaviors such as swimming. The aim of this study was to determine the effects of hookworms (Uncinaria sp.) on the development of swimming capabilities in A. australis through physiological and ethological analyses.
- Higher parasite burden was associated with reduced growth rates and lower blood hemoglobin concentrations, whereas scaled body mass and blood hemoglobin levels had an important positive effect on the water activity of the pups. However, antihookworm treatment did not affect the level of water activity of the pups, and pups with high hookworm burden increased their time budget in water. This was probably related to lower maternal attendance in heavily parasitized pups, leaving these pups more time to perform water activities. Therefore, pups with heavy hookworm burden, despite having decreased growth rates and blood hemoglobin concentrations, compensated for their handicap in physiological traits related to swimming by spending more time in the water.
- This work offers new insights to understand the contrasting effects of parasites on aquatic organisms, and the compensatory mechanisms employed by infected animals to avoid the worst consequences of parasitism.
12.
Charles R. Knapp Caro Perez‐Heydrich Trevor T. Zachariah Jill Jollay Amy N. Schnelle Sandra D. Buckner Christine R. Lattin L. Michael Romero 《Ecology and evolution》2019,9(4):1946-1956
Investigations focusing on host–ectoparasite interactions in animals have revealed asymptomatic to severe health and fitness consequences suggesting that species mobilize different interspecific response mechanisms. Fewer studies, however, have examined intraspecific responses to ectoparasitic burdens. In this study, we analyzed host health and fitness responses to increasing ectoparasite burdens along with the presence/absence of hemoparasites of free‐ranging insular rock iguanas (Cyclura cychlura) in The Bahamas. Using hematology, plasma biochemistry, as well as body condition and growth rate comparisons, we failed to find significant associations of tick burdens with annual growth rate, corticosterone, packed cell volume, total white blood cell, and heterophil, monocyte, eosinophil or hemoglobin measures. We did, however, find mixed and significant associations of tick burdens with lymphocyte and basophil counts, heterophil‐to‐lymphocyte ratios, and body condition indices. These associations varied by sex, size, and hemoparasite infection status suggesting that different life stages of iguanas may invest differently in immune responses, and impacts may be modulated based on size and sex of hosts, and coinfection status. 相似文献
13.
Rebecca L. Taylor Mark S. Udevitz Chadwick V. Jay John J. Citta Lori T. Quakenbush Patrick R. Lemons Jonathan A. Snyder 《Marine Mammal Science》2018,34(1):54-86
The Pacific walrus (Odobenus rosmarus divergens) is a candidate to be listed as an endangered species under United States law, in part, because of climate change‐related concerns. While the population was known to be declining in the 1980s and 1990s, its recent status has not been determined. We developed Bayesian models of walrus population dynamics to assess the population by synthesizing information on population sizes, age structures, reproductive rates, and harvests for 1974–2015. Candidate models allowed for temporal variation in some or all vital rates, as well as density dependence or density independence in reproduction and calf survival. All selected models indicated that the population underwent a multidecade decline, which began moderating in the 1990s, and that annual reproductive rate and natural calf survival rates rose over time in a density‐dependent manner. However, selected models were equivocal regarding whether the natural juvenile survival rate was constant or decreasing over time. Depending on whether juvenile survival decreased after 1998, the population growth rate either increased during 1999–2015 or stabilized at a lesser level of decline than seen in the 1980s. The probability that the population was still declining in 2015 ranged from 45% to 87%. 相似文献
14.
The composition of predator adipose stores can provide important insights into foraging patterns and the ecological relationships among species. We determined the fatty acid (FA) composition of 843 blubber samples from 80 bearded seals (Erignathus barbatus), 33 harbor seals (Phoca vitulina), 239 harp seals (Pagophilus groenlandicus), 32 hooded seals (Cystophora cristata), 281 ringed seals (Phoca hispida), 53 walruses (Odobenus rosmarus rosmarus), 105 beluga whales (Delphinapterus leucas), and 20 narwhals (Monodon monoceros) across the Canadian Arctic to examine patterns of variability among and within species. FA signatures accurately distinguished phocid seals, walruses, and whales. Belugas and narwhals had the most similar FA signatures of any two species, suggesting substantial overlap in their diets, especially in the narwhal‐wintering area off eastern Baffin Island. Among phocid seals, harp and hooded seals had the most similar FA signatures. Bearded seals were most similar to walruses, which was consistent with the benthic feeding habits of both species. Within species, geographic differences in FA signatures were found over both large (>4,000 km) and small (<100 km) spatial scales. Overall, within‐species differences were smaller than among‐species differences. In general, FA signature patterns were consistent with previous studies of the ecology and diets of arctic marine mammals. 相似文献
15.
Pest monitoring methods should provide unbiased accurate estimates of pest densities and locations, while also minimizing time‐in‐field and costs. Recent pest mammal monitoring studies have found that chew cards are more effective than conventional mammal monitoring methods, but little experimental work has been done to determine optimal experimental duration or quantify the risks of saturation by one species biasing detections of other species. Here, we used chew cards in three sites within Awarua wetland (Southland, New Zealand) to investigate the optimal amount of time required to detect targeted pest species (rats, possums and mice), and to examine the potential of rats and possums to bias detection rates of other species. We found depressed detections of possums and rats where a contraspecific had been detected on a card, which is consistent with previous studies of a similar duration on interspecies interference. This experiment is the first to analyse the rates at which species detections accrue over the course of a survey, and we found rat detections lagged behind possums for the first four nights. We modelled the effect of survey duration and relative rat abundance on the likelihood of further possum detections. Duration and rat abundance interacted, meaning there are trade‐offs to be considered with regard to duration: shorter durations may avoid the risk of saturation in areas of high pest density, but risk not sampling sparse or neophobic populations. Our data suggest that chew cards remain one of the most sensitive pest monitoring tools for rats and possums, compared to conventional methods such as tracking tunnels and wax tags. In areas of moderate pest densities, we suggest that a duration of five nights is optimal for detecting pests. However, in areas of high pest density the sensitivity of chew cards may render them unsuitable because of saturation and interspecies interference effects. 相似文献
16.
Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals. 相似文献
17.
Almir R. Pepato Teofnia H. D. A. Vidigal Pavel B. Klimov 《Ecology and evolution》2019,9(23):13359-13374
18.
Marcelo Lopes Rheingantz Victor Manuel Santiago‐Plata Cristine Silveira Trinca 《Mammal Review》2017,47(4):291-305
- The Neotropical otter Lontra longicaudis is a widespread semiaquatic carnivore living in a wide variety of environments in both fresh‐water and salt‐water ecosystems. We summarise the current knowledge on distribution, ecology, behaviour, evolution and conservation status of the species, and highlight the main threats that have been affecting it as well as priority actions for securing its survival.
- The current geographical range of Lontra longicaudis is discussed, as well as several efforts that have been made to update knowledge of the range. Throughout its known distribution area, the Neotropical otter has high genetic diversity, and recent molecular research suggests that variations in genetic diversity are related to geography. Taxonomic issues regarding the existence of subspecies persist, mainly due to limited sampling in key portions of the species’ range.
- Although the Neotropical otter is widely distributed in Latin America and has flexible behaviour, it is subjected to a variety of threats, which lead this otter to be officially considered Threatened in several countries within its geographical range.
- The species still faces an uncertain future due to the impact of human activities, thus justifying its classification as Near Threatened in the International Union for Conservation of Nature's Red List. The real level of human‐otter conflicts and the impact of modified environments on Neotropical otter populations are still unclear, and must be a priority focus of future studies.
- There is an urgent need to increase our knowledge on aspects of the Neotropical otter's biology, such as reproduction, generation time, behaviour, physiology, distribution limits, sanitary aspects, evolution and taxonomy. Understanding these topics is vital to ensure the long‐term survival of the species, both at the local and at the regional scale, as well as to provide the basis for environmental education actions involving local riverside human communities
19.
Qamar A. Schuyler Chris Wilcox Kathy A. Townsend Kathryn R. Wedemeyer‐Strombel George Balazs Erik van Sebille Britta Denise Hardesty 《Global Change Biology》2016,22(2):567-576
Plastic marine debris pollution is rapidly becoming one of the critical environmental concerns facing wildlife in the 21st century. Here we present a risk analysis for plastic ingestion by sea turtles on a global scale. We combined global marine plastic distributions based on ocean drifter data with sea turtle habitat maps to predict exposure levels to plastic pollution. Empirical data from necropsies of deceased animals were then utilised to assess the consequence of exposure to plastics. We modelled the risk (probability of debris ingestion) by incorporating exposure to debris and consequence of exposure, and included life history stage, species of sea turtle and date of stranding observation as possible additional explanatory factors. Life history stage is the best predictor of debris ingestion, but the best‐fit model also incorporates encounter rates within a limited distance from stranding location, marine debris predictions specific to the date of the stranding study and turtle species. There is no difference in ingestion rates between stranded turtles vs. those caught as bycatch from fishing activity, suggesting that stranded animals are not a biased representation of debris ingestion rates in the background population. Oceanic life‐stage sea turtles are at the highest risk of debris ingestion, and olive ridley turtles are the most at‐risk species. The regions of highest risk to global sea turtle populations are off of the east coasts of the USA, Australia and South Africa; the east Indian Ocean, and Southeast Asia. Model results can be used to predict the number of sea turtles globally at risk of debris ingestion. Based on currently available data, initial calculations indicate that up to 52% of sea turtles may have ingested debris. 相似文献
20.
As the global trend towards urbanization continues, the need to understand its impact on wildlife grows. Species may have different levels of tolerance to urban disturbance; some even appear to thrive in urban areas and use human‐subsidized resources. However, the physiological costs and trade‐offs faced by urban‐dwelling species are still poorly understood. We assess the evidence for a negative impact of urbanization on the Black Sparrowhawk Accipiter melanoleucus, a raptor that recently colonized Cape Town, South Africa, and explore the potential mechanisms behind any such effect. We predicted that birds in more urbanized areas may be in poorer health and that this may be partially driven by differences in prey quantity and quality along an urban habitat gradient. The health of Black Sparrowhawk nestlings was evaluated through measures of their physiological stress (heterophil/lymphocyte ratio), body condition and blood parasite infection (infection risk and intensity of Haemoproteus and Leucocytozoon). Diet composition was determined through an analysis of prey remains collected around nests, and prey abundance was determined through point counts in different habitat types. We could find no negative effects of urbanization on nestling health, with no significant relationships with heterophil/lymphocyte ratio, body condition, risk and intensity of infection by Haemoproteus or intensity of infection by Leucocytozoon. Risk of infection by Leucocytozoon did, however, decline with increasing urban cover, perhaps because urbanized areas contain less habitat for blackflies, the vectors of this parasite, which require moving fresh water. We found no change in diet breadth or composition with increasing urban cover. Although some prey species were abundant or less abundant in certain habitat types, all habitat types contained ample prey for Black Sparrowhawks. The widespread abundance of food resources and resulting lack of nutritional stress may explain why Black Sparrowhawks are seemingly free of the negative health impacts expected to arise from urbanization. These findings may explain the success of the species in Cape Town and suggest that for urban‐dwelling, bird‐eating raptors the abundance of prey in cities may override any potential negative impacts of urbanization on health due to disturbance or other sources of stress. 相似文献