Henrique C. Giacomini, Mauro Galetti, An index for defaunation, Biological Conservation, Available online 16 May 2013, ISSN 0006-3207, 10.1016/j.biocon.2013.04.007.
Defaunation, originally conceived as the loss of large vertebrates due to hunting or fragmentation, has been widely used in conservation studies yet the term has been arbitrarily used and poorly defined. Here we refine this term by creating a quantitative index that can be used to compare ecological communities over large zoogeographical regions. We propose a defaunation index (D) as a weighted measure of dissimilarity between the current assemblage of a given location and a reference assemblage that represents a historical and/or unperturbed state. We analyzed the index by means of three case studies that included two empirical assessments of mammal communities in Neotropical rainforests and one hypothetical example, encompassing a variety of criteria to quantify differences in species density and importance. These cases illustrate the broad range of index applicability and show that incorporating functional differences among species, such as those based on body size, conservation status or evolutionary originality can add important information beyond simply species richness.
Alexandre M. Martin, Hélène Presseault-Gauvin, Marco Festa-Bianchet, Fanie Pelletier
Male mating competitiveness and age-dependent relationship between testosterone and social rank in bighorn sheep
Behavioral Ecology and Sociobiology, June 2013, Volume 67, Issue 6, pp 919-928
In males, the acquisition and development of behavioral and morphological secondary sexual traits typically depends on testosterone and correlates with mating success. Testosterone level could affect competition for mates and thus be a target of sexual selection. We sought to relate testosterone levels to male mating competitiveness, by teasing apart the relationships between testosterone, behavior, and growth before the mating period. We monitored 24 adult bighorn rams (Ovis canadensis) at Ram Mountain, Alberta, from 2008 to 2011. Using linear mixed models, we tested the relationships between testosterone metabolites in feces, social rank, and both growth and size of two sexually selected traits: horns and body mass. The correlation between testosterone and social rank varied with age. Testosterone and rank were weakly and negatively correlated for young rams, positively correlated for prime-aged rams, and negatively correlated for older rams. Although testosterone had an increasingly positive effect on total horn length until 8 years of age, we could not detect any effects on annual growth rate of horns or body mass. Testosterone may be related to male’s ability to compete for mates through its relationship with behaviors determining social rank, rather than by influencing the development of morphological traits. Differences in testosterone levels among competitors may be a proximate cause of variance in fitness.
Hongliang Dou, Guangshun Jiang, Philip Stott, Renzhu Piao
Climate change impacts population dynamics and distribution shift of moose (Alces alces) in Heilongjiang Province of China
Ecological Research, May 2013
The earth is experiencing obvious climate warming, which may impact population dynamics and the distribution of moose (Alces alces). In this study, we examined the effects of density dependence, temperature, snow depth, and the vegetation (NDVI) on the population dynamics of moose in Heilongjiang Province of China using historical data. Our results demonstrated that moose distribution had continued to contract from the 1980s to the 1990s; moose densities and late spring temperatures in the 1980s were negatively correlated to the rate of increase of the moose population; low and high snow depths in the 1990s showed positive and negative effects, respectively, on the rate of population increase; and the effect of NDVI in the 1980s was similar to the effect of snow depth. Therefore, we confirmed that moose population dynamics is influenced both by intrinsic density-dependent and extrinsic habitat factors, especially late spring temperatures. In addition, an increase in late spring temperatures may shift the southern limit of the distribution of the moose northwards, or may isolate the southernmost portion of the moose population because the rate of warming is higher to the north of a present latitudinal constriction in range than it is at the latitude of the southernmost moose.
May 2013 Birth-year and current-year influences on survival and recruitment rates of female Weddell seals
Glenn E. Stauffer, Jay J. Rotella, Robert A. Garrott
In long-lived species, juvenile survival typically is lower and more variable than adult survival, and modeling such variation is important for understanding population dynamics. Variability in juvenile survival can be related to birth- or current-year influences, and the birth-year influences can be transient, persistent, or intermediate in duration. We used multi-state models and data collected from 5,459 known-aged prebreeder female Weddell seals (Leptonychotes weddellii Lesson) tagged in Erebus Bay, Antarctica from 1980–2007 to evaluate the duration of potential birth-year influences on survival rates and the importance of birth- and current-year influences on survival and recruitment rates. Survival rates differed for each birth cohort and were positively related to current-year winter sea-ice conditions. The estimated duration of birth-cohort effects on survival was intermediate (6 years) rather than transient (2 years) or permanent. Estimated survivorship from birth to 6 years of age varied among cohorts from 0.13 (SE = 0.04) to 0.42 (SE = 0.06), and averaged 0.25 (SE = 0.02). Recruitment rates (probability of transitioning from prebreeder to breeder state) varied annually but apparently were not related to birth-year conditions. Our results provide evidence that birth- and current-year conditions act in combination to influence survival. Although for many long-lived species the influences of either birth- or current-year conditions on survival are well-studied, we suggest that modeling survival rates as a function of birth- and current-year influences simultaneously could lead to better understanding of survival and improved stochastic models to project population dynamics.
Population Trends and Reproduction of Bald Eagles at Besnard Lake, Saskatchewan, Canada 1968–2012
François Mougeot, Jon Gerrard, Elston Dzus, Beatriz Arroyo, P. Naomi Gerrard, Connie Dzus, and Gary Bortolotti
Journal of Raptor Research 2013 47 (2), 96-107
The study of population regulation is crucial for understanding population dynamics and for conservation. We report on trends in population size and reproduction of Bald Eagles (Haliaeetus leucocephalus) at Besnard Lake, Saskatchewan, Canada, during 1968–2012. We investigated the relative importance of density-dependent (population size) and density-independent (climate) factors in explaining variation in population growth rate and productivity. The number of occupied Bald Eagle territories increased until ca. 1988, but remained stable afterwards, fluctuating around ca. 26 pairs. The number of successful pairs increased until only ca. 1977 and remained relatively stable or slightly declined afterwards (ca. 16 successful breeding pairs per year). We found a strong negative density-dependence in all reproduction parameters (mean productivity, nesting success, mean brood size at fledging). Annual production initially increased in the 1970s, but decreased afterwards, while nesting success decreased throughout the whole study period. We also found a strong density-dependence in population growth rate, indicating that the stabilized population was regulated. It probably reached its carrying capacity in the late 1970s, although population size continued to increase until the late 1980s. Mean brood size at fledging was negatively related to the number of failed nesting pairs. Density alone explained most of the variation in breeding performance, although milder springs were weakly associated with a higher nesting success. Finally, we found evidence for regular fluctuations in mean productivity, and particularly in nesting success, with a 5-yr period. We discuss possible mechanisms behind the observed patterns of density-dependent reproduction and implications for our knowledge of how this eagle population is regulated.
Sibling Competition Induces Stress Independent of Nutritional Status in Broods of Upland BuzzardsReuven Yosef, Sundev Gombobaatar, and Gary R. Bortolotti
Journal of Raptor Research 2013 47 (2), 127-132
In any evaluation of the health and well-being of wildlife, whether to test biological theory or evaluate conservation problems, it is imperative to know to what degree variables are operating independently. Too often, important ecological and physiological traits such as body mass, immune function, and blood parameters may have a common agent influencing them; one example is glucocorticoids (corticosterone in birds) secreted in response to environmental stressors. We evaluated the nutritional condition of broods of Upland Buzzards (Buteo hemilasius) in Mongolia using ptilochronology, a measure of growth rate of feathers, and the amount of corticosterone in feathers as a long-term integrated measure of the response to stressors. Absolute amount of feather corticosterone was not significantly related to food supply, attributes of the brood, or feather growth rate. However, the relative amount of corticosterone of junior nestlings vs. their senior siblings increased as the age difference between them increased. Similarly, in the study area with larger broods where more sibling competition likely existed, junior siblings showed relatively higher amounts of stress. Our results suggested that stress seemed to be associated with sibling conflicts, and not a product of the consequences of the nutritional condition of the individuals.
The Effect of Introduced Species on Raptors
Karina L. Speziale and Sergio A. Lambertucci
Journal of Raptor Research 2013 47 (2), 133-144
Biological invasions are considered one of the major threats to the Earth’s biota, and their prevention and control are widely recommended. A critical step is to gather information on the effects of introduced species on native species. In such analysis, it is important to consider both the negative effects and the fact that many nonnatives have become key components of existing ecosystems. The effects of nonnatives are particularly worrisome for raptors because raptors have high trophic positions and their ecological role can structure native communities. We here examine the effects of introduced species on raptors, as well as the interest in studying these effects, through a review of the published literature. The numbers of studies on raptors and introduced species as individual topics are rapidly increasing, but despite this we found few articles relating the two topics and fewer still with a clear aim of studying this relationship. Although the number of published reports we found was low, articles indicating negative effects outnumbered articles showing positive ones. Negative effects identified included decrease in native prey and direct or indirect poisoning via poisons aiming to protect productive introduced species from predators or to control introduced pests. Positive effects identified included extension of distributional range facilitated by introduced species or nonnative species as a food source. Very importantly, native raptors can become dependent on introduced species, and any proposed control of the nonnative/introduced species merits careful evaluation. In conclusion, the effects of nonnative species on this key group of top predators and scavengers have been poorly considered, but merit special attention and specific design in future studies.
Winter Ranges of Migratory Turkey Vultures in Venezuela
Erik M. Hedlin, C. Stuart Houston, Philip D. McLoughlin, Marc J. Bechard, Marten J. Stoffel, David R. Barber, and Keith L. Bildstein
Journal of Raptor Research 2013 47 (2), 145-152We used four Global Positioning System (GPS) satellite transmitters to calculate the wintering ranges of migratory Turkey Vultures (Cathartes aura) that breed in Saskatchewan, Canada, and winter in Venezuela. Between 2007 and 2011, 95% fixed-kernel estimators of range size varied from 54 to 76 731 km2 with an average of 16 814 ± 28 606 km2 (SD), while those calculated with 95% Minimum Convex Polygons ranged from 22 to 46 778 km2 and averaged 9545 ± 17 356 km2. The smallest wintering range was comparable to previously reported range sizes, but our largest wintering range greatly exceeded anything yet recorded. Variation in winter range sizes may be attributed to resource availability, migration costs, and the absence of obligations associated with breeding. Each vulture had a “primary nocturnal roost” to which it returned frequently; each spent more hours (evenings, nights, and mornings) at and within 1 km of such roosts, than it did foraging during midday. Our results increased our understanding of the feeding and movement ecology of North American migratory Turkey Vultures overwintering in South America.
Turkey Vulture Breeding Behavior Studied with Trail Cameras
Chloë E. Rollack, Karen Wiebe, Marten J. Stoffel, and C. Stuart Houston
Journal of Raptor Research 2013 47 (2), 153-160
We report initial findings on Turkey Vulture (Cathartes aura) breeding behavior from nests in abandoned buildings in Saskatchewan. We used infrared trail cameras placed at three nests between 2009 and 2011 and we also present anecdotal information from several other nests. Some parents could be identified and differentiated by their patagial tags and satellite transmitter backpacks. In two years, a pair of tagged vultures successfully evicted a prospecting pair from a nest site that the tagged pair had used in the previous year. However, another vulture was observed at four sites in four years, suggesting that breeders are not always philopatric. The trail cameras revealed that additional vultures occasionally roosted on nest buildings of the focal pair, and occasionally entered the nest space during incubation; whether these individuals participated in the nesting activities or were only prospecting for nest sites was unclear. We describe nest preparatory activities and three contexts for the spread-wing posture in Turkey Vultures. Both sexes participated in incubation on alternate days, and the eggs were sometimes left unattended for up to 5 hr. Both parents also fed nestlings at a frequency of 1–4 total feeds per day. Monitoring of patagial-tagged vultures revealed four individuals breeding as 6- and 7-yr-olds, at an earlier age and with greater dispersal distances from the natal nest than previously reported. These preliminary findings illustrate the value of trail cameras as an effective tool to monitor and describe the breeding biology of Turkey Vultures.
Feather Corticosterone Levels and Carotenoid-Based Coloration in Common Buzzard (Buteo buteo) Nestlings
Jesús Martínez-Padilla, François Mougeot, Jesús T. García, Beatriz Arroyo, and Gary R. Bortolotti
Journal of Raptor Research 2013 47 (2), 161-173
Most of our understanding of the function of colored traits displayed by birds and the mechanisms that produce or maintain them comes from studies on adults. However, colored traits are often displayed by nestlings from a young age, and these traits may influence parent-offspring interactions or sibling competition. The mechanisms that may mediate the expression of those traits during growth are still fairly unknown in raptors. In this study, we examined a possible mediating effect of corticosterone levels on the expression of carotenoid-pigmented traits in nestlings of Common Buzzards (Buteo buteo), specifically the yellow-orange coloration of their cere and legs. We assayed corticosterone levels deposited in feathers, which can provide a reliable and integrated index of stress responses during growth. Carotenoids can be used to color integuments, or diverted to other physiological processes involved in self-maintenance. We hypothesized that corticosterone levels mediate how carotenoids can be diverted to functions other than coloration. We show that carotenoid and corticosterone levels were positively associated, perhaps because of a higher metabolic activity in more-stressed nestlings. Corticosterone levels were negatively correlated with the coloration of cere and legs in females only. Altogether, our results support the hypothesis that corticosterone may influence how carotenoid pigments are allocated for needs other than coloration, although in a sex-specific manner. We encourage further studies exploring how individuals cope with and respond to stressful conditions, in order to better understand the complex interactions between corticosterone, carotenoids, and coloration during nestling growth.
Carotenoids and Skin Coloration in a Social Raptor
Julio Blas, Sonia Cabezas, Jordi Figuerola, Lidia López, Alessandro Tanferna, Fernando Hiraldo, Fabrizio Sergio, and Juan J. Negro
Journal of Raptor Research 2013 47 (2), 174-184
The outcome of social and sexual competition in animals is typically mediated through the expression of body traits. Conspicuous characters such as yellow, orange, and red colorations in skin, scales, and feathers are often posited as quality-dependent signals, because such colors are made of dietary carotenoids and their use for signaling conflicts with health functions. Raptors often lack brightly colored feathers but most diurnal species display intense orange and yellow hues in the cere and legs. Here we test the hypothesis that integument coloration functions as a signal of status in wild raptors, revealing availability of carotenoid pigments. As study model we used the Black Kite (Milvus migrans), a highly social, long-lived, and sexually monogamous Accipitriform. Regular trapping of adults throughout the breeding season revealed that circulating carotenoid levels were highest in breeding males, whereas breeding females and floaters showed moderate and statistically similar carotenoid titers. Plasma levels of carotenoids showed a slight seasonal decline, especially marked in post-laying females. Leg and cere colorations were visually assessed through comparison to a color chart, yielding a very high interobserver reliability and consistency with simultaneous spectrophotometric measures. Integument color was similar between the sexes, brighter in breeders compared to floaters, and positively related to circulating carotenoids, but only in the floaters. These results suggest that the physiological regulation of signal expression is different in breeders and floaters, possibly involving a costly social or physiological mechanism that ensures the honesty of coloration as a quality-dependent signal. In addition, breeding males and females displayed similar color scores despite strong differences in plasma carotenoids, indicating sex-related differences in physiological regulation that were not apparent in floaters. Our results are consistent with a role of integument coloration in status signaling in wider competitive contexts than those enforced by sexual selection. The reported patterns of coloration can be ultimately explained by two alternative, non-mutually exclusive hypotheses: (1) the lower coloration displayed by floaters reflects underlying physiological limitations and mediates the access to breeding resources through social competition (constraint hypothesis), and young floaters have evolved mechanisms to restrain color expression and thus signal their competitive inferiority, avoiding physiological and social costs (restraint hypothesis).
Brightness Features of Visual Signaling Traits in Young and Adult Eurasian Eagle-OwlsChiara Bettega, Letizia Campioni, María Del Mar Delgado, Rui Lourenço, and Vincenzo Penteriani
Journal of Raptor Research 2013 47 (2), 197-207
Recent research has demonstrated the important role of visual communication in nocturnal birds. Achromatic plumage patches (i.e., pigment-free white feathers) with high levels of contrast against dark backgrounds are excellent candidates for visual signaling in the dark or at twilight, when differences in color may be less effective. In this study, with the goal of investigating the signaling role of certain achromatic plumage patches, we examined the characteristics and patterns of the brightness (i.e., total reflectance) of Eurasian Eagle-Owl (Bubo bubo) white feather patches for both young birds and adult individuals. Our results showed that (1) the total reflectance of young birds‘ white feathers differed significantly from that of adult owls‘ white feathers; the brightness differed between the sexes in adults only, with females showing a significantly higher reflectance than males; the total reflectance of the white patch around a young bird’s mouth was positively correlated with brood size; the total reflectance of the white badge on the throat of adults was positively correlated with their hematocrit values; an assortative mating scenario based on the brightness of an individual’s white badge was deemed possible; and we did not detect any significant relationship in the levels of reflectance for related individuals: the young and their parents were not found to be distinguishable based on the brightness of their white feather patches.
Nest-Box Occupancy by Neotropical Raptors in a Native Forest of Central Argentina
M. Soledad Liébana, José H. Sarasola, and Miguel Á. Santillán
Journal of Raptor Research 2013 47 (2), 208-213
Breeding populations of raptors are sometimes limited by nest-site availability and the use of nest boxes to bolster such populations is widespread. In the neotropical forest, little is known about the ecology of cavity-nesting raptors and their use of nest boxes. Here we examine occupancy patterns of nest boxes by five raptor species during eight years in a semiarid forest of central Argentina: the American Kestrel (Falco sparverius), the Spot-winged Falconet (Spiziapteryx circumcincta), the Tropical Screech-Owl (Megascops choliba), the Barn Owl (Tyto alba), and the Ferruginous Pygmy-Owl (Glaucidium brasilianum). We analyze the influence of vegetation type on nest-box selection, report cases of nest usurpation, and present information on the breeding rates of some of these species. The raptor species showed a marked selection for nest boxes surrounded by grassland, where hunting success may be higher, and avoided those nest boxes placed in habitats dominated by dense shrublands. We observed two cases of nest usurpation (i.e., a species takes over active nests of another species for breeding purposes), in which two different boxes were occupied almost simultaneously by the Ferruginous Pygmy-Owl and the American Kestrel.
Jungfer, K.-H., Faivovich, J., Padial, J. M., Castroviejo-Fisher, S., Lyra, M.L., Berneck, B.V.M., Iglesias, P.P., Kok, P. J. R., MacCulloch, R. D., Rodrigues, M. T., Verdade, V. K., Torres Gastello, C. P., Chaparro, J. C., Valdujo, P. H., Reichle, S., Moravec, J., Gvoždík, V., Gagliardi-Urrutia, G., Ernst, R., De la Riva, I., Means, D. B., Lima, A. P., Señaris, J. C., Wheeler, W. C., Haddad, C. F. B. (2013). Systematics of spiny-backed treefrogs (Hylidae: Osteocephalus): an Amazonian puzzle. —Zoologica Scripta, 00, 000–000.
Spiny-backed tree frogs of the genus Osteocephalus are conspicuous components of the tropical wet forests of the Amazon and the Guiana Shield. Here, we revise the phylogenetic relationships of Osteocephalus and its sister group Tepuihyla, using up to 6134 bp of DNA sequences of nine mitochondrial and one nuclear gene for 338 specimens from eight countries and 218 localities, representing 89% of the 28 currently recognized nominal species. Our phylogenetic analyses reveal (i) the paraphyly of Osteocephalus with respect to Tepuihyla, (ii) the placement of ‘Hyla’ warreni as sister to Tepuihyla, (iii) the non-monophyly of several currently recognized species within Osteocephalus and (iv) the presence of low (<1%) and overlapping genetic distances among phenotypically well-characterized nominal species (e.g. O. taurinus and O. oophagus) for the 16S gene fragment used in amphibian DNA barcoding. We propose a new taxonomy, securing the monophyly of Osteocephalus and Tepuihyla by rearranging and redefining the content of both genera and also erect a new genus for the sister group of Osteocephalus. The colouration of newly metamorphosed individuals is proposed as a morphological synapomorphy for Osteocephalus. We recognize and define five monophyletic species groups within Osteocephalus, synonymize three species of Osteocephalus (O. germani, O. phasmatus and O. vilmae) and three species of Tepuihyla (T. celsae, T. galani and T. talbergae) and reallocate three species (Hyla helenae to Osteocephalus, O. exophthalmus to Tepuihyla and O. pearsoni to Dryaderces gen. n.). Furthermore, we flag nine putative new species (an increase to 138% of the current diversity). We conclude that species numbers are largely underestimated, with most hidden diversity centred on widespread and polymorphic nominal species. The evolutionary origin of breeding strategies within Osteocephalus is discussed in the light of this new phylogenetic hypothesis, and a novel type of amplexus (gular amplexus) is described.
Gierl C, Reichenbacher B, Gaudant J, Erpenbeck D, Pharisat A (2013) An Extraordinary Gobioid Fish Fossil from Southern France. PLoS ONE 8(5): e64117. doi:10.1371/journal.pone.0064117
The classification of gobioid fishes is still under discussion. Several lineages, including the Eleotridae and Butidae, remain difficult to characterize because synapomorphies are rare (Eleotridae) or have not yet been determined (Butidae). Moreover, the fossil record of these groups is scarce.
Exceptionally well-preserved fish fossils with otoliths in situ from uppermost Oligocene sediments (≈23–24 Mio. y. ago) in Southern France provide the most in-depth description of a fossil gobioid to date. The species was initially described as Cottus aries Agassiz, then transferred to †Lepidocottus Sauvage, and subsequently assigned to Gobius. Based on a comparative analysis of meristic, osteological and otolith data, this species most likely is a member of the family Butidae. This discovery is important because it represents the first record of a fossil butid fish based on articulated skeletons from Europe.
The Butidae and Eleotridae are currently distributed in W-Africa, Madagascar, Asia and Australia, but they do not appear in Europe and also not in the Mediterranean Sea. The new results indicate that several species of the Butidae thrived in Europe during the Oligocene and Early Miocene. Similar to the recent Butidae and Eleotridae, these fishes were adapted to a wide range of salinities and thrived in freshwater, brackish and marginal marine habitats. The fossil Butidae disappeared from Europe and the Mediterranean and Paratethys areas during the Early Miocene, due probably to their lack of competitiveness compared to other Gobioidei that radiated during this period of time. In addition, this study documents the great value of otoliths for gobioid systematics.