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Trichoptera and several other insect orders have evolved functional diptery while retaining four wings (morphological tetraptery), which results from the interaction of specialized structures that unite the wings. In this contribution, the comparative and functional morphology of the forewing-hindwing coupling apparatuses and related structures in the suborder Integripalpia are presented. The components of the wing coupling apparatuses have varied and complex morphologies and interaction modes, that result in partial to complete wing coupling. Wing coupling has evolved repeatedly within the infraorders Brevitentoria and Plenitentoria, and the morphologies of the wing coupling apparatuses are synapomorphies for several families. Phylogenetic trends are discussed that relate to the evolution of functional diptery, such as the diminution of forewing jugal lobes and hindwing prehumeral setae, reinforcement of wing veins, changes in vein topology and elaboration of wing surface features. A novel at-rest forewing-forewing coupling apparatus that has also evolved repeatedly is described and related to the evolution of wing coupling.
Nest predation in ground nesting black grouse (Tetrao tetrix) inhabiting managed boreal forests is arguably the single most important cause of nesting failure. Little is known, however, about indirect effects of other factors, such as maternal or environmental properties, and to what extent maternal and habitat qualities interact with varying levels of predator densities. Using an information-theoretical approach, we studied maternal and environmental determinants of daily nest survival rates under variable predator densities of 210 individual black grouse hens in central Finland. Environmental determinants were far more important than maternal ones, and the effects were more apparent at higher predator densities. Keeping predator densities constant, daily nest survival rates increased with nest conspicuousness and increasing tree density, and were higher in undrained areas. While there was no difference between adults and juveniles, hens that invested more in egg size were more successful. Therefore, environmental factors and, to a lesser extent, maternal properties, indirectly affect nesting success especially when predator density is high. Modern forestry practices such as clear cutting and drainage are commonly linked to increased densities of predators such as foxes. Our results suggest that the nesting success of black grouse may further be indirectly affected by the same practices, the overall impact being a balance between the negative (e.g. drainage, clear-cutting) and the positive (reforestation, producing dense young forest stands) effects.
Daily defecation rate is an important variable in density estimation of African (Loxodonta qfricana) and Asian (Elephas maximus) elephants. However, there has been no attempt to construct a general model that predicts defecation rates. By comparing 16 published studies, we found that annual and seasonal daily defecation rates increased with annual rainfall following a power regression model. We recommend calculating defecation rates based on the regressions from our meta-analysis, rather than using a defecation rate from any single study.
Eurasian otters, top predators of freshwater ecosystems, are food limited; thus, species conservation plans should consider local food resources. We used spraint (faecal) analysis to assess diet of otters inhabiting a river in the Polish Carpathians. Although elsewhere in their range otters feed mostly on fish, in our study area amphibians were equally important prey (43% of all prey occurrences, 54% of estimated biomass of consumed prey). Amphibians dominated in the otter diet in winter and spring, and occurred as often as fish in autumn. Only in summer was amphibian occurrence marginal. Typically, two factors explain seasonally high consumption of amphibians: limited fish availability and availability of amphibians gathered to spawn or hibernate. However, factors such as energetic costs of hunting may also cause seasonal changes in otter feeding behavior. Low water temperatures might increase the energetic cost of fishing in cold seasons and force otters to seek an alternative prey. This study raises the possibility that amphibian declines could negatively affect otters in cold, mountainous regions.
The fur of mammals serves many functions, including thermoregulation, camouflage or visual signaling to conspecifics. Fine-scale features of fur, such as hair morphology are often examined by researchers, especially in animals where pelage is of economic importance. Certain studies from this literature body show that males of many species appear to have thicker guard hair than females. Here, we examined this possibility in coyote (Canis latrans) and white tailed deer (Odocoileus virginianus) from captive populations in Utah and Georgia, USA. We used image analysis procedures to examine 402 guard hairs from 24 captive coyotes and 568 guard hairs from 29 captive deer, measuring the length and diameter of each hair. In both species, males had significantly thicker hairs than females; in coyotes, male hairs were 17% thicker, in deer, male hairs were 15% thicker. These differences are comparable to other species, where male hair is between 7%–20% thicker than those of females (in all species the average difference is 13%). Considering that there are hundreds of thousands of hairs on any given animal, this difference per unit hair could translate into considerable differences in overall pelt characteristics between sexes. The reason for this difference could relate to the sensitivity of mammalian hair to androgens, such as testosterone, which are more abundant in males of all species. Experimental studies and population surveys demonstrate that high levels of androgens stimulate body hair to grow thicker in diameter. Thus, the greater levels of testosterone in males would act to promote thicker hair. By this same mechanism, within any given collection of males, those with greater levels of androgens should also display greater hair thickness. While further research would be needed to verify this, results from this study nevertheless emphasize the knowledge gaps that yet remain in our understanding of the basic nature of mammalian fur.
Natural selection affects emotional and behavioural patterns, such as anti-predator adaptations, that enhance human survival. Fear is a basic emotion that activates behavioural responses upon encountering a predator, being consistently higher in females than in males. In this study, we investigated associations between fear of a large carnivore predator and perceived physical condition in a sample of Slovakian participants (n = 943). When testing evolutionary hypotheses explaining gender differences in fear of predators, we found partial support for the “physical condition” hypothesis, because females either reported lower perceived body condition than males and their perceived body condition showed significant correlation with fear of brown bear, Ursus arctos. The negative association between fear and perceived body condition was stronger in males suggesting that fear evolved as a response to higher predation pressures on males in our evolutionary past, indirectly supporting the “predation pressure” hypothesis. Males and participants with higher fear of bears wanted to exterminate bears by shooting more than others, suggesting that future management strategies should be oriented on elimination of fear of predators, as primary predictor of extremely negative attitudes toward bears.