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471.
Brett R. Panting Eric M. Gese Mary M. Conner Scott Bergen 《The Journal of wildlife management》2021,85(1):97-108
Pronghorn (Antilocapra americana) occur throughout western North America. In Idaho, USA, following intensive hunting to reduce crop depredations in the late 1980s, pronghorn populations have not rebounded to desired levels. Because neonatal survival in ungulates is one factor limiting population growth, we evaluated cause-specific mortality and the influence of intrinsic and extrinsic factors on survival rates of 217 radio-collared pronghorn fawns across 3 study areas in Idaho during 2015–2016. For intrinsic variables, we determined the sex and body mass index (BMI) for each fawn. For extrinsic variables, we determined the abundance of predators and alternate prey, estimated the normalized difference vegetation index (NDVI) for 1 month pre- and post-parturition, and measured fecal nitrogen and diaminopimelic acid (DAPA). We considered NDVI as a measure of plant productivity, and fecal nitrogen and DAPA as possible proxies of diet quality. We predicted NDVI, fecal nitrogen, and DAPA would be positively related to the nutritional status of females and positively related to fawn survival. We used Program MARK with known fate models to estimate semi-monthly survival rates of pronghorn fawns for the first 4 months post-parturition. During both years, the leading cause of fawn mortality was coyote (Canis latrans) predation (58%), followed by unknown causes of mortality (18%), unknown predation (12%), predation by bobcats (Lynx rufus; 6%), predation by golden eagles (Aquila chrysaetos; 3%), and other (3%). Mean fawn survival for the 4 months post-parturition across years and study sites was 0.42 ± 0.04 (SE; range = 28–62%). The top survival model included BMI, lagomorph abundance, and DAPA and had a model weight of 83.3%. All 3 variables were positively related to pronghorn fawn survival. Because females with increased nutrition generally have heavier fawns, BMI was likely correlated to diet quality, which was supported by the positive relationship between DAPA and fawn survival. We hypothesize that high lagomorph abundance created an alternate prey base to buffer coyotes from preying on pronghorn neonates. We found no influence of measures of NDVI (pre- and post-parturition), fecal nitrogen, or predator abundance on fawn survival. Management actions providing high-quality forage for pronghorn are likely to contribute to production of heavier fawns having the highest chance of survival. © 2020 The Wildlife Society. 相似文献
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473.
William H. Conner James G. Gosselink Roland T. Parrondo 《American journal of botany》1981,68(3):320-331
Net primary productivity and community structure were studied at three adjacent swamp sites that were all once subject to seasonal flooding. Because of man-related activities one is now permanently flooded, and a second is managed on a summer-fall dry period and a winter-spring flooded period. In the permanently flooded area such flood-intolerant trees as green ash are dying while shrubs and aquatic plants are increasing. Competition among overstory trees is reduced, enhancing growth of existing baldcypress and water tupelo trees. Total areal production, however, is low (887 g/m2/yr) because of fewer trees. Productivity in the managed area is high (1,780 g/m2/yr). The baldcypress-water tupelo community is being replaced by a swamp maple-ash community typical of bottomlands. In the natural swamp forest, baldcypress and water tupelo have remained dominant. Canopy closure has limited understory and aquatic growth but has also increased competition among overstory trees, resulting in a slow increase in basal area. Productivity is about 1,166 g/m2/yr. It is suggested that the flooding regime is an important controlling factor in each of the areas. 相似文献
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475.
Essential nutrients and toxicants often coexist in the diet of humans and animals. Interactions among nutrients and chemicals in the diet may alter the toxicity of the chemical or the requirement for or availability of specific nutrients. Such interactions have been demonstrated among toxins and dietary protein, trace elements, and vitamins. Certain nutrients may also alter the response to certain drugs, and some drugs, such as oral contraceptives, may alter the availability of some nutrients. The carcinogenicity of some compounds and the subsequent promotion of tumor growth are affected by nutrients such as fat, vitamins, and lipotropes and by such minor dietary constituents as naturally occurring indoles and synthetic preservatives. In this paper we review such interactions as well as the mechanisms responsible for them. 相似文献
476.
The polka-dot wasp moth,Syntomedia epilais Wlk. (Lepidoptera, Arctiidae, Ctenuchinae), engages in extensive acoustic signaling during courtship. The signals, which are produced by both sexes, consist of sexually dimorphic trains of ultrasonic clicks. Field and laboratory behavioral experiments demonstrated that (1) sound production from both the male and the female is required for mating success, (2) femaleS. epilais show a higher level of acoustic responsiveness to male acoustic signals than to female signals, and (3) males use the female acoustic signals to locate their potential mates. It is suggested that the existence of the system is made possible by a reduction in bat predation pressure, perhaps the result of extreme distastefulness combined with the distinctive acoustic image that flying ctenuchines present to foraging bats. 相似文献