Decrease in body size of Danish goshawks during the twentieth century

Recent studies indicated that body size of various animals, including birds, changed during the twentieth century, and these changes were attributed to changes in food availability and climate. We used museum skins of goshawks (Accipiter gentilis) collected between 1854 and 1941 and between 1979 and 1998 in order to check whether body size of this species in Denmark changed during the study period. We compared three body measurements (wing, beak and tarsus length) and the first principal component (PC1) derived from these measurements of four groups of goshawks (adult and immature, females and males). We found that the wing length of goshawks collected after 1979 was significantly smaller in comparison with those collected before this year, and females were more affected than males. Immature birds (but not adults) collected after 1979 had significantly shorter beaks than those from the early period. Immature females collected after 1979 had shorter tarsi than those collected in the early period. There was a significant decrease in body size (as represented by PC1) from the early to late period, which was more pronounced among females and immature birds. In conclusion, body size of goshawks in Denmark decreased during the twentieth century.     

Recent increase in body size of the American marten Martes americana in Alaska

Using museum specimens, we studied recent changes in skull size of the American marten Martes americana , in continental Alaska. In Alaska, global warming has resulted in milder winters that may contribute to an improved food supply in the wild. In the present study, we tested the hypothesis that body size of the marten had increased during the second half of the 20th century, in response to global warming. We found that skull size, and by implication body size, increased significantly during the second half of the 20th century, possibly due to an improved food supply and/or lower metabolic demands in winter. Improved food availability in winter may result from the improved nutritional conditions for prey, and/or from increased access to prey resulting from a longer snow-free season. Longitude had a significant positive effect on skull size and a significant negative effect on teeth size. In Alaska, the climate is milder along the western coast and becomes harsher inland. Hence, the milder climate was associated with larger body size providing further support for our prediction that body size of the American marten was influenced by food availability and reduced energy expenditure. The negative relationship between longitude and teeth size may indicate a trend towards a larger prey in inland marten populations, but we have no data to support or refute this hypothesis.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 701–707.     

No recent temporal changes in body size of three Danish rodents

We used museum collections to study temporal trends of possible changes in skull size, body mass and body length in three species of rodents in Denmark. Skulls of adult Microtus agrestis, Apodemus flavicollis and Apodemus sylvaticus, collected between 1895 and 2004, 1847 and 2002, and 1895 and 2002, respectively, were measured and data on body mass and length were taken from the museum registers. Principal component (PC) analysis was used to combine data of the four skull measurements taken. We tested the relationship of sex, latitude, longitude, month and year of collection to PC1 by a General Linear Model (GLM). PC1, body length and body mass of M. agrestis significantly increased from west to east. In addition, PC1, body mass and body length of M. agrestis declined from summer (August) through autumn and winter to spring (March), probably due to the decline in food availability towards winter. None of the other factors examined (sex, latitude and year) were significantly related to body size. PC1 of A. flavicollis and A. sylvaticus was not significantly related to any of the environmental factors examined.     

Decline in American marten occupancy rates at Sagehen Experimental Forest,California

We compared the distribution and frequency of American marten (Martes americana) detections during historic surveys and a recent survey on the Sagehen Experimental Forest (SEF) in the Sierra Nevada Mountains, California. This area has been the location of 9 previous marten surveys during 1980–1993, each involving a systematic detection/non-detection survey on the same grid. These data are a time series of information on the occupancy of martens that can be related to habitat change in the study area. Our objectives were to 1) resurvey martens in SEF using methodology similar to previous studies to assess current marten occupancy; 2) evaluate changes in marten occupancy during the period 1980–2008; and 3) examine associations between marten occurence and changes in habitat and landscape metrics. Current marten occupancy was estimated using surveys conducted in summer 2007, winter 2007–2008, and summer 2008. From 1978 to 2007 there was a decrease in predicted habitat patch size, core area, and total amount of marten habitat in the study area, as well as an increase in distance between patches. Marten detections in 2007–2008 were approximately 60% lower than in surveys in the 1980s. We detected no martens in the summers of 2007 and 2008, and 10 detections in winter 2007–2008 were limited to higher elevations in the southwestern portion of SEF. No martens were detected in the lower elevations where most of the recent forest management activity occurred. We suggest that the marten population at SEF has been negatively affected by the loss and fragmentation of habitat. We recommend that future management of forests in the Sagehen basin focus on restoring and connecting residual marten habitat to improve habitat quality for martens. © 2011 The Wildlife Society.     

Changes in size of Baltic field voles over the last 50 years: are they really shrinking?

Using museum materials and recently trapped specimens of field voles (Microtus agrestis (Linnaeus, 1761)) from Lithuania and Estonia, we assessed temporal and latitudinal trends in body and skull size, comparing the periods 1980–1996 and 2014–2016. We measured four body and 23 skull characters, size-adjusting them using the geometric mean procedure. A pronounced decrease in the size of M. agrestis was noted in Estonia, where 23 out of 27 adjusted body and skull characters had decreased by up to 21.9%, with only the tail length, hind foot length, maximum height of mandibula excluding coronoid process and coronoid height of mandibula increasing significantly. Decreases were less marked in voles from Lithuania – most pronounced were a 6.1% decrease in adjusted body length, an 11.6% decrease in adjusted length of the braincase, a 3.85% decrease in the breadth of the braincase, measured at the widest part, a 2.9% decrease in condylobasal skull length and a 2.2% decrease in the height of the braincase. The coronoid height of the mandibula of Lithuanian individuals showed an 8.4% size increase. In both countries, the confounding effect of sex on the size changes of M. agrestis from 1980 to 2016 was much smaller than the effect of time period. Concluding, voles in Estonia became significantly smaller, while changes in the measured characters in Lithuania were heterogeneous.     

Where to sleep in a rural landscape? A comparative study of resting sites pattern in two syntopic Martes species

The niche‐complementarity hypothesis predicts that two sympatric species must differ in their requirements for one of the three main ecological dimensions (i.e. habitat use, diet, and activity time) to coexist. European pine marten Martes martes and stone marten M. foina are syntopic medium‐sized mustelids with very similar morphology and ecology for which resting sites are a key resource. To better understand how these species coexist, we investigated whether key features of their resting site pattern (number of resting sites, area over which they are distributed, main habitat type used for resting) differed. We used diurnal telemetry to identify resident individuals (e.g. spatially stable individuals over time) and to locate them during resting periods in a fragmented forested area in France. Stone marten used fewer resting sites distributed over a smaller surface area than pine marten. Most stone marten resting sites were located in open habitat (83%) in the proximity of human habitations, whereas pine martens rested almost exclusively in forest (98%). Sex, age, and season explained some variability in both the number of resting sites and the probability of resting within forested habitat for stone marten but not pine marten. The area covered by resting sites was larger in males than in females, but age modulated this difference in an opposite way for the two species. Such a pattern was expected given the intra‐sexual territoriality and the reproductive phenology of these species. Overall, stone marten showed higher inter‐individual variability in resting site pattern than pine marten. The particular pattern observed in subadult male stone martens during summer (increase in resting site surface area and in the probability to rest in forest) may reflect an attempt to settle in forests, and we discuss these implications in the context of interspecific competition.     

Intraguild dietary overlap and its possible relationship to the coexistence of mesocarnivores in intensive agricultural habitats

The stone marten (Martes foina) and the pine marten (M. martes) are closely related mammalian carnivores potentially subject to exploitative competition. The recent expansion of the pine marten into the intensively cultivated plain of the River Po (NW Italy), where previously only stone marten occurred, offered an interesting opportunity to analyse their relationships. We studied the distribution and diet of Martes species and trophic niche overlap between martens and red foxes (Vulpes vulpes) in two study areas, each with two pseudoreplicates, by analysing genotyped faeces. Our results seem to confirm the displacement of the stone marten from one study area, the pine marten being the only Martes species occurring where previously the stone marten had been reported. We found a large food niche overlap between red fox and both stone and pine martens, but with evidence of size-related differences in the consumption of some food items. We hypothesised that, due to the poor prey-base of the environment, highly altered by intensive crop cultivation, intense interspecific competition originally occurred between the red fox and stone marten. The heightening of interspecific competition caused by the entry of the pine marten in the predator guild may have caused the displacement of the stone marten, at least temporarily. The mechanism of such displacement needs to be clarified through further surveys in areas where the three species occur sympatrically.     

Patch occupancy by stone martens Martes foina in fragmented landscapes of central Spain: the role of fragment size,isolation and habitat structure

We studied the response to forest fragmentation of a generalist carnivore, the stone marten Martes foina, in highly fragmented landscapes of central Spain. Five different areas (n = 178 fragments) in central Spain were surveyed. This paper analyses the relationship between fragment use by martens (measured through scat presence) and a series of variables related to the size, isolation and vegetation structure of each fragment by means of stepwise logistic regression. Size and isolation have an important effect on stone marten presence in fragments. Our results were similar to those found for other marten species in landscapes with coarse-grain fragmentation, but they contrast with other studies conducted in landscapes with fine-grain fragmentation. These data suggested that in highly fragmented landscapes, size and isolation factors resulting from forest fragmentation were responsible for determining marten responses, irrespective of their habitat generalism. Management policies for the stone marten in highly fragmented scenarios require the maintenance of large forests near continuous forest tracts in mountains or riparian woodlands.     

Body size of the weasel Mustela nivalis and the stoat M. erminea in Sweden

In this study we examined temporal and geographical variations in a sample of 124 skulls of the weasel Mustela nivalis and 146 skulls of the stoat M. erminea, collected in Sweden between 1959-1992 and 1913-1990, respectively.We used Principal Component Analysis (PCA) to combine the effects of latitude, longitude, year of collection, mean ambient temperature and Net Primary Productivity (NPP). The first principal component (PC1) contained latitude, ambient temperature and NPP and was significantly and positively related to male (but not female) skull size of both stoats and weasels. None of the other factors or their interactions were significantly related to skull size.We conclude that ambient temperature, either directly through energy savings, or indirectly through improved food availability (increased NPP), had a significant effect on determining body size of male stoats and weasels in Sweden. Our results support the hypothesis that male and female of these species are affected by different selection pressures and thus react differently to changing environmental conditions.     

Relationships among allozyme heterozygosity, morphology and lipid levels in house sparrows during winter

House sparrows ( Passer domesticus ) were collected during cold (43 individuals) and warm (31 individuals) periods in February 1982 from farms near Lawrence, Kansas. Fat scores (from flank, rump and furcula) and body mass were measured from the carcasses, which were then reduced to skeletons. Heterozygosity was determined by electrophoresis of three polymorphic allozymes. Pectoral lipid content was determined by petroleum ether extraction. Principal component (PC) analysis was conducted on 14 skeletal measurements. Summed fat score, body mass and pectoral lipid content served as dependent variables in three multiple regressions. Sex, period (cold versus warm), number of heterozygous loci (0–3), and scores of PCI, PC2 and PC3 were independent variables. Each of the dependent variables was also included as an independent variable in regressions in which they were not the dependent variable. Pectoral lipid content was significantly related only to the number of heterozygous loci (R²= 0.18, P = 0.008). Summed fat score differed between sexes and periods ( P = 0.012 and 0.001, respectively) when body mass was included in the regression ( P < 0 001). Body mass was related to summed fat score as above, and also to body size (PCI, P < 0.0001) and period ( P = 0.014). Females exhibited a positive regression between body size and summed fat score ( P = 0.007). Body size (PCI) was greater for both sexes in the sample from the warm period ( P = 0.022), suggesting that selection for increased body size may have occurred. Increased metabolic efficiency of heterozygous enzymes or individuals is suggested as an explanation for the observed relationship between heterozygosity and intramuscular lipid level.     

Do well-connected landscapes promote road-related mortality?

Cost surface (CS) models have emerged as a useful tool to examine the interactions between landscapes patterns and wildlife at large-scale extents. This approach is particularly relevant to guide conservation planning for species that show vulnerability to road networks in human-dominated landscapes. In this study, we measured the functional connectivity of the landscape in southern Portugal and examined how it may be related to stone marten road mortality risk. We addressed three questions: (1) How different levels of landscape connectivity influence stone marten occurrence in montado patches? (2) Is there any relation between montado patches connectivity and stone marten road mortality risk? (3) If so, which road-related features might be responsible for the species’ high road mortality? We developed a series of connectivity models using CS scenarios with different resistance values given to each vegetation cover type to reflect different resistance to species movement. Our models showed that the likelihood of occurrence of stone marten decreased with distance to source areas, meaning continuous montado. Open areas and riparian areas within open area matrices entailed increased costs. We found higher stone marten mortality on roads in well-connected areas. Road sinuosity was an important factor influencing the mortality in those areas. This result challenges the way that connectivity and its relation to mortality has been generally regarded. Clearly, landscape connectivity and road-related mortality are not independent.     

Observations on variation in skull size of three mammals in Israel during the 20th century

Among mammals, food availability, especially during the growth period, is a key predictor in determining final body size, and improved nutrition may lead to an increase in their body size. In Israel during the last century food availability for animals commensal with humans increased greatly, due to a 16-fold increase in the human population and the accompanying changes, such as a 135-fold increase in the area of irrigated agriculture and the availability of large quantities of organic garbage.Using museum material, we studied temporal changes in skull size of a sample of 89 red foxes (Vulpes vulpes Linnaeus, 1758), 108 golden jackals (Canis aureus Linnaeus, 1758) and 117 Cape hares (Lepus capensis Linnaeus, 1758) collected during the 20th century. Four measurements (condylobasal length, zygomatic breadth, the length of the upper cheek teeth row and the length of the mandible) were taken for each skull, and principal component analysis was used to combine the measurements into principal components.We found that skull size of the red fox increased significantly during the 20th century, possibly due to improved food availability from man-made resources such as agricultural produce and garbage. No temporal trend in body size was detected for the jackal and hare. These differences are discussed.     

Nest temperature, incubation period, and investment decisions of incubating wood ducks Aix sponsa

Incubating birds must balance their energetic demands with the time needed to provide care to developing embryos. Reduced care by incubating parents can result in longer incubation periods that increase predation risk and potentially influence neonate phenotype. We measured nest temperature, incubation period, and body mass dynamics of female wood ducks Aix sponsa , and used an information-theoretic approach to investigate effects of several explanatory variables on incubation period and thermal characteristics of nests. A model that included clutch size and standard deviation of nest temperature best explained the variation in incubation period. Parameter estimates indicated that incubation period increased with increases in clutch size and standard deviation of nest temperature. Next, we examined relationships between maternal effects and the standard deviation of the nest temperature. The best fitting model included initiation date of incubation. There was little support for including early incubation body mass of females, incubation constancy, and percent change in female body mass in the model. The parameter estimate showed that standard deviation of nest temperature declined as initiation date of incubation advanced. Female body mass at the start of incubation was not related to structural size suggesting that heavy females were in better physical condition than were light females. Heavy females nested earlier and lost more body mass during incubation than light females, but heavy females did not reduce variation in nest temperature to decrease the incubation period. The fact that early nesting females in good physical condition did not shorten incubation periods by keeping nest temperatures less variable could have been due to either energetic limitations or restraints. Experimental manipulations of incubation costs will be needed to distinguish between these hypotheses.     

Geographic variation in body size: the effects of ambient temperature and precipitation

Latitudinal trends in body size have been explained as a response to temperature- or water-related factors, which are predictors of primary production. We used the first principal component calculated from three body parameters (weight, body length and the greatest length of the skull) of a sample of mammals from Israel and Sinai to determine those species that vary in size geographically, and whether such variation is related to annual rainfall, average minimum January temperature and average maximum August temperature. We used a conservative approach to discern the effects of precipitation and temperature by applying sequential regression. Variable priorities were assigned according to their bivariate correlation with body size, except for rainfall and its interactions that entered into the model last. Eleven species (Acomys cahirinus, Apodemus mystacinus, Canis lupus, Crocidura suaveolens, Gerbillus dasyurus, Hyaena hyaena, Lepus capensis, Meles meles, Meriones tristrami, Rousettus aegyptius and Vulpes vulpes) of the 17 species examined varied in size geographically. In five of them, rainfall was positively related to body size, while in one species it was negatively related to it. Contrary to the prediction of Bergmann’s rule, mean minimum January temperature was positively related to body size in five species and negatively related to body size in two species (C. suaveolens and G. dasyurus). As predicted by Bergmann’s rule, maximum June temperature was negatively related to body size in three species, and positively so in one (L. capensis). Primary production, particularly in desert and semi-desert areas, is determined mainly by precipitation. The above results indicate that, in our sample, primary production has an important effect on body size of several species of mammals. This is evident from the considerable proportion of the variability in body size explained by rain. However, low ambient temperatures may slow down and even inhibit photosynthesis. Hence, the observed positive relationships between average minimum January temperature and body size in four of the six species influenced by rain further support this conclusion.     

Bergmann’s rule for Neomys fodiens in the middle of the distribution range

The body size of Palearctic Sorex shrews decreases at higher latitudes, and as such the Bergmann’s rule does not work. However, no analysis has ever been done for water shrew (Neomys fodiens) in the middle of distribution range. Analysis of available literature data showed that some body and skull measurements of N. fodiens are negatively correlated to latitude. Measurements of 158 water shrews from Estonia and Lithuania were also analyzed with respect to the short scale latitudinal pattern. We found that populations are separated (Wilk’s lambda = 0.363, p<0.0001). Differences are related to PC1 (skull size), explaining 49.80% of the variance and PC2 (body size), explaining 10.06% of the variance. Estonian shrews are smaller in their body and skull (most differences significant) and their skulls are relatively shorter and wider in the area of the brain case. Thus, the negative correlation of body and skull size to latitude in N. fodiens is applicable even over quite short latitudinal distances. Further analysis of diagnostic characters between N. fodiens and N. anomalus is required.     

Body size of the red fox Vulpes vulpes in Spain: the effect of agriculture

The body size of animals is affected by several factors, including ambient temperature and food availability. Ambient temperature is often negatively related to body size (Bergmann's rule) whereas an improved diet, especially during growth, has a positive effect. Animals commensal with man commonly exploit additional food sources (e.g. garbage dumps), thereby increasing their food supply. Using museum material, we studied morphological variation in skull size (and thus body size) among Spanish red foxes. Four measurements were taken of each skull and were related to the habitat from which the foxes were collected (agricultural and non-agricultural), and to latitude as a proxy for ambient temperature. The skull size of foxes collected in agricultural areas during the late 20th Century was significantly larger than that of those from non-agricultural areas, and was negatively related to latitude, thus contradicting Bergmann's rule. We suggest that increased food availability from animal husbandry is the cause for the observed increase in skull size (and thus body size).  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 729–734.     

大蹄蝠头骨形态地理变化

本文采用几何形态测量法对中国大蹄蝠9个不同地理种群头骨形态变化进行研究。结果表明,不同地理种群的头骨大小及形状存在显著差异,其中云南思茅种群与海南陵水种群差异最大。回归分析表明头骨形态的地理变化与气候因素相关。随着年均温度、年均湿度的升高以及年均降水量的增多,大蹄蝠头骨变小,上颌、齿、咬肌附着部分以及耳蜗部分的形状发生变化。此外,头骨大小与海拔高度呈正相关,头骨形状变化与纬度显著相关。本研究表明对栖息地生态条件的适应是中国大蹄蝠头骨形态地理变化的重要原因。     

Far from the madding crowd: Tolerance toward human disturbance shapes distribution and connectivity patterns of closely related Martes spp.

To assess niche overlap between the most similar European sympatric carnivores, the pine marten Martes martes and stone marten Martes foina, and outline their potential distributions and connectivity corridors in Central Italy, we applied a multivariate kernel density procedure which allowed to assess both species' ecological hypervolumes based on a set of 16 environmental predictors and used the resulting probability of occurrence map as a resistance surface in electrical circuit theory-based models. Distance to watercourses and percent cover of deciduous forest and shrubland were the most relevant factors shaping pine marten ecological niche, while stone marten distribution was mainly shaped by human population density and cover of both human settlements and deciduous forest. Overlap between the hypervolumes of the two martens was low-to-moderate, while, on average, landscape connectivity was higher for the stone marten. The inclusion in the models of human disturbance-related variables enabled to define a possible mechanism driving habitat partitioning in human-altered landscapes. Based on our results, increasing human density and urbanization of European lowland and hilly landscapes are expected to represent a greater threat to the pine marten than the stone marten.     

Accumulation and dissemination of prion protein in experimental sheep scrapie in the natural host

Background  

Since 1954, there have been in excess of 800 cases of rabies as a result of European Bat Lyssaviruses types 1 and 2 (EBLV-1, EBLV-2) infection, mainly in Serotine and Myotis bats respectively. These viruses have rarely been reported to infect humans and terrestrial mammals, as the only exceptions are sheep in Denmark, a stone marten in Germany and a cat in France. The purpose of this study was to investigate the susceptibility of foxes to EBLVs using silver foxes (Vulpes vulpes) as a model.     

Selection in a cycling population: differential response among skeletal traits

Abstract Population density cycles influence phenotypic evolution through both density‐dependent selection during periods of high density and through enhanced genetic drift during periods of low density. We investigated the response of different phenotypic traits to the same density cycles in a population of the yellow‐necked mouse, Apodemus flavicollis, from Bia?owieza National Park in Poland. We examined nonmetric skull traits, skull and mandible size, skull and mandible shape, and transferrin allele frequencies. We found that all of the traits changed significantly over the seven‐year study period. The greatest changes in nonmetric traits and mandible size occurred during periods of increasing density, and the magnitude of changes in skull and mandible shape was correlated with the magnitude of density changes. Frequencies of transferrin alleles changed the most when population density was in decline. Changes among the five phenotypic traits were generally uncorrelated with one another, except for skull and mandible shape. Nonmetric traits were selectively neutral when assessed with Q_ST/F_ST analysis, whereas mandible size, mandible shape, and skull shape showed evidence of fairly strong selection. Selection on skull size was weak or nonexistent. We discuss how different assumptions about the genetic components of variance affect Q_ST estimates when phenotypic variances are substituted for genetic ones. We also found that change in mandible size, mandible shape, skull size, and skull shape were greater than expected under a neutral model given reasonable assumptions about heritability and effective population size.