Age Classes Of Females Research Articles

Causes and consequences of pre-hibernation body mass in golden-mantled ground squirrels (Callospermophilus lateralis)

Abstract Mammals that cope with harsh environmental conditions by hibernating show seasonal variation in body mass, as fat reserves are accumulated during summer and depleted during winter. In hibernating species, pre-hibernation mass is often considered a key phenotypic trait that can influence future survival and reproductive success—yet we know little about how variation in environmental conditions and seasonality affect pre-hibernation mass. We used 30 years of demographic data from a high-elevation population of golden-mantled ground squirrels (Callospermophilus lateralis) to identify life history and environmental variables that influenced pre-hibernation mass in females. Additionally, we determined if pre-hibernation mass influenced overwinter survival or subsequent reproduction. Growth curves revealed female-biased size dimorphism in body mass; adult mass was not attained until age 2 years, so we considered 3 age classes of females: juveniles, yearlings, and adults (≥2 years). We found that earlier snow melt during spring is associated with higher subsequent pre-hibernation body mass for yearlings and adults, and that juveniles emerging earlier from their natal burrows had higher pre-hibernation masses than later-emerging juveniles. Estimates of food quantity or quality did not affect pre-hibernation mass for any age class, nor was there an effect of reproductive status. Juvenile females with greater pre-hibernation mass were more likely to survive overwinter and reproduce as yearlings, but we found no such effect for yearlings or adult females. We did not find an effect of snow depth or winter duration on either survival or reproduction. Our results indicate that time appears to be the key variable for golden-mantled ground squirrels to acquire sufficient body mass to survive and reproduce, but the effects vary by age class.

Validating enzyme immunoassays for non-invasive reproductive hormone monitoring in Temminck's pangolin.

Gonadal hormones play a central role in reproductive function and success. As such, quantifying reproductive hormones non-invasively in threatened, vulnerable and endangered wildlife species offers an ideal tool for assessing general and individual reproductive patterns in situ. Whilst the use of faeces as a hormone matrix is often preferred in these cases, the required enzyme immunoassays (EIAs) for measuring faecal androgen (fAM), oestrogen (fEM) and progestagen metabolite (fPM) concentrations must first be validated if a species gets investigated for the first time to ensure biologically relevant patterns can be observed. In this study we aimed to biologically validate the EIAs for monitoring fAM, fEM and fPM concentrations in Temminck's pangolin, Smutsia temminckii. Hormone metabolite concentrations derived from each EIA tested were compared between different age and sex classes. An epiandrosterone EIA effectively measured androgen levels in males, distinguishing between adult and juvenile individuals, as well as both female age classes. Similarly, the tested oestrogen EIA successfully distinguished between adult and juvenile female fEM concentrations, and both tested progestagen EIAs demonstrated adequate differences between fPM concentrations of adult and juvenile females. The now-validated EIAs offer robust tools for a non-invasive monitoring of reproductive activity in Temminck's pangolin. The development of such techniques will allow researchers to assess reproductive hormone patterns of the species in situ, whilst also paving the way for further studies in this field. Despite the small sample size due to the species' conservation status, the study provides a foundation for future research using a robust, validated, non-invasive monitoring tool. The latter can now be implemented in long-term monitoring with larger sample sizes to yield more comprehensive data, aiding in the conservation of Temminck's pangolin.

Growth, weights, and measurements of female wild sheep from Iran

Abstract Wild sheep (Ovis spp.) are of conservation concern throughout the Middle East. Little is known, however, about the natural history or ecology of this taxon. To better understand size relationships among wild sheep occupying Iran, we analyzed results from 120 females collected from widely separated ecosystems. Morphometrics and body weights for all age categories of females occupying the Khosh-Yeilagh Wildlife Refuge in northeastern Iran were larger than those for the same age classes of females occupying Bamou National Park in southwestern Iran. Females from Bamou National Park, however, obtained adult body weight (x̅ = 25.8 ± 2.47 [SD] kg) at an earlier age than those from the Khosh-Yeilagh Wildlife Refuge (x̅ = 36.6 ± 3.21 kg). Ecological differences between these two areas suggest that net primary productivity, which is a function of numerous climatic and geographical factors, has been a primary force contributing to these results. Weights and measurements reported here provide the basic information for additional, more detailed research necessary to fully understand the evolutionary significance and management implications of these differences in body size and emphasize the conservation value of even the most basic natural history information.

Factors associated with the mass of eggs laid by tree swallows Tachycineta bicolor varied yearly between 2008 and 2016 in Michigan

The initial investment a female bird makes in an offspring is her production of its egg. The size of this investment can have important evolutionary consequences for both the female and her offspring. Between 2008 and 2016, we weighed 1977 tree swallow eggs freshly laid in nest boxes in west Michigan to investigate factors associated with egg mass. Breeding female age class was not associated with egg mass. Overall, eggs that hatched weighed significantly more than those that did not. An egg's mass was not associated with clutch size but increased with its position in the laying sequence. Females that bred multiple times showed high repeatability of egg mass. Mother–daughter narrow sense heritability of egg mass was low. There were statistically significant associations, both positive and negative, between female morphological characteristics and egg mass in some years but not others. Similarly, relationships between egg mass and weather conditions during egg formation were statistically significant in some years but not others. In summary, female characteristics and weather conditions were associated with tree swallow egg mass, but their influences varied yearly. These results reinforce the importance of long‐term studies for identifying the causes of selection that shape life‐history characteristics.

Reliability of External Characteristics to Age Barrow's Goldeneye

ABSTRACTAccurate assignment of age class is critical for understanding most demographic processes. For waterfowl, most techniques for determining age class require birds in hand, reducing utility for quickly and efficiently sampling a large portion of the population. As an alternative, we sought to establish an observation‐based methodology, achievable in the field with standard optics, for determining age class of Barrow's goldeneyes (Bucephala islandica). We photographed heads, wings, and bellies of 232 Barrow's goldeneyes captured during late winter (February–April) of 2007–2015 along the north Pacific Coast. From these photographs, we focused on 5 external characteristics for both males and females, with binary states that putatively corresponded to 2 age classes—first‐year birds (<1 yr) and adults (>1 yr). For males, all 5 external traits (belly color, head color, eye color, facial crescent, median secondary coverts color) had binary states that were reliably distinguishable by observers. Moreover, all 5 external traits were highly predictive of age class (≥96% concordance between external vs. bursal‐derived ages), and novice observers, after receiving training, were able to accurately age 96% of first‐year and 99% of adult males. In contrast, patterns were weaker for females; putative external characteristics of female age class (belly color, bill radiance, bill blackness, eye color, median secondary coverts color) had 77–91% concordance with bursal‐derived age, compared with 96–100% for males, and observers misidentified age classes of 15% of females, compared with only 2% of males. Overall, age classes of male Barrow's goldeneyes were accurately and reliably distinguishable during winter based on several external characteristics, whereas those of females were not. Our technique may be used to estimate age composition of male Barrow's goldeneyes during winter, providing a useful metric for monitoring annual changes in adult‐to‐juvenile ratios and other important demographic parameters. © 2020 The Wildlife Society.

Understanding invasion success of Pseudorasbora parva in the Qinghai-Tibetan Plateau: Insights from life-history and environmental filters

Understanding mechanisms of fish invasion success is crucial to controlling existing invasions and preventing potential future spread. Despite considerable advances in explaining successful fish invasions, little is known about how non-native fish successfully invade alpine freshwater ecosystems. Here, we explore the role of fish life history and environmental factors in contributing to invasion success of Pseudorasbora parva on the Qinghai-Tibet Plateau. We compared life history trait differences between native populations in lowland China with introduced populations in lowland Europe and the high elevation Qinghai-Tibet Plateau. Linear mixed-effects models were used to analyse life-history trait variation across elevation gradients. A random forest model was developed to identify the key environmental filters influencing P. parva invasion success. Life history characteristics differed substantially between native and introduced populations. Compared with native Chinese populations, introduced populations in lowland Europe had smaller body size, higher fecundity, smaller oocytes and earlier maturation. Introduced populations in the Qinghai-Tibet Plateau had smaller body size, lower fecundity, smaller oocytes and later maturation compared with native populations. 1-Year-Length and fecundity in all age classes of females significantly increased with increasing elevation. 2-Year-Length and 3-Year-Length of male significantly increased while maximal longevity and length at first maturity were significantly decreased with the elevation gradient. Habitat type, annual mean temperature, elevation, annual precipitation and precipitation seasonality, were the 5 most important predictors for the occurrence of the P. parva. Our study indicates that invasive P. parva adopt different life history strategies on the plateau compared with invasive populations at low elevations, highlighting that more studies are required for a better understanding of biological invasion under extreme conditions. Considering the ongoing hydrologic alteration and climate change, our study also highlighted that P. parva may expand their distribution range in the future on the Qinghai-Tibet Plateau.

Demographic Tipping Points as Early Indicators of Vulnerability for Slow-Breeding Megafaunal Populations

Decisions based on trends in population abundance and distribution may fail to protect populations of slow-breeding, long-lived megafauna from irrevocable decline if they ignore demographic constraints. For such taxa, we suggest that understanding the interactions among vital rates governing population growth rates be prioritized over predicting probabilities of extinction. The proximity of a population to the demographic tipping points, i.e. where growth rate switches from positive to negative, can signal vulnerability to perturbation long before numbers drop below a point of no return. We define the “demographic safe space” as the combination of key vital rates that support a non-negative growth rate and illustrate this approach for Asian elephants. Using modeling, we find that even with optimal reproduction, Asian elephant populations cannot tolerate annual female mortality rates exceeding 7.5%. If adult mortality is very low (3% / yr), populations can tolerate high annual mortality in calves below age 3 (up to 31.5% / yr), or slow female reproduction (primiparity at 30 years or average inter-birth interval of up to 7.68 years). We then evaluate potential impact of current threats, showing that near-optimal reproduction and high calf survival is necessary to offset even modestly increased mortality among adult female age classes. Rather than rely on simple counts or “viability” assessments, we urge that conservation resources for slow-breeding megafauna also be invested in identifying demographic tipping points and how to maintain populations within their safe spaces.

Can concentrations of steroid hormones in brown bear hair reveal age class?

Although combining genetic and endocrine data from non-invasively collected hair samples has potential to improve the conservation of threatened mammals, few studies have evaluated this opportunity. In this study, we determined if steroid hormone (testosterone, progesterone, estradiol and cortisol) concentration profiles in 169 hair samples collected from free-ranging brown bears (Ursus arctos) could be used to accurately discriminate between immature and adult bears within each sex. Because hair samples were acquired opportunistically, we also needed to establish if interactions between hormones and several non-hormone factors (ordinal day, year, contact method, study area) were associated with age class. For each sex, we first compared a suite of candidate models by Akaike Information Criteria model selection, using different adult-age thresholds (3, 4 and 5 years), to determine the most supported adult age. Because hair hormone levels better reflect the endocrine state at an earlier time, possibly during the previous year, then at the time of sampling, we re-analysed the data, excluding the records for bears at the adult-age threshold, to establish if classification accuracy improved. For both sexes, candidate models were most supported based on a 3-year-old adult-age threshold. Classification accuracy did not improve with the 3-year-old bear data excluded. Male age class was predicted with a high degree of accuracy (88.4%) based on the concomitant concentrations of all four hormones. Female age class was predicted with less accuracy (77.1%) based only on testosterone and cortisol. Accuracy was reduced for females, primarily because we had poor success in correctly classifying immature bears (60%) whereas classification success for adult females was similar to that for males (84.5%). Given the small and unbalanced sample used in this study, our findings should be viewed as preliminary, but they should also provide a basis for more comprehensive future studies.

Europe-wide consistency in density-dependence of red deer (Cervus elaphus) fertility

Population dynamics of large herbivores are affected by density dependent and density independent processes. Changing population size causes variation in age- and sex-specific demographic parameters such as reproduction, survival and dispersal. With our study, based on meta-analyses of literature data, we aimed at (1) describing age-specific fertility rates of red deer (Cervus elaphus) throughout Europe, and (2) tracking negative density feedback in reproduction of female red deer. Across the species range, in most European populations (84%) females began breeding as yearlings. We observed age-specific variation in female fertility, which was the lowest and most diverse in yearling females. Increasing population density had a negative effect on female fertility in all age groups. There was no difference in the strength of the relationship between different age classes of females. In 1.5-year old females, at low and moderate densities, fertility exhibited a high variation, which could indicate strong susceptibility of youngest females to detrimental external factors. Our study showed that meta-analysis of Europe-wide data was able to detect biologically relevant relationships which may be difficult to observe when applying locally-based and time-scale approach.

Courtship sequence and evidence of volatile pheromones inPhasgonophora sulcata(Hymenoptera: Chalcididae), a North American parasitoid of the invasiveAgrilus planipennis(Coleoptera: Buprestidae)

AbstractPhasgonophora sulcataWestwood (Hymenoptera: Chalcididae) is a North American parasitoid now usingAgrilus planipennisFairmaire (Coleoptera: Buprestidae) as a novel host, and may prove useful in biocontrol. Unfortunately, information is lacking regarding mating and the presence of pheromones, which may be important when attempting to exploit this parasitoid within a management context. Herein we used olfactometer assays and behavioural observations to determine the courtship and mating sequences ofP. sulcata.A significantly higher proportion of males oriented towards females over the control arm containing filtered air in an olfactometer regardless of the age classes of females or males examined. We also observed four pre-copulatory behaviours that were consistent in all mating pairs. Our results indicate that courtship may be mediated by male perception of female-produced pheromones. Understanding the courtship sequence may be useful in rearing laboratory populations, while the putative pheromones may be useful in detection and retention ofP. sulcatapopulations.

Reindeer management and winter pastures in the presence of supplementary feeding and government subsidies

We apply an age- and sex-structured reindeer-lichen model to examine the role of winter pastures, pasture rotation, and supplementary feeding on economically optimal reindeer management. The model includes 17 age classes of females, 13 classes of males and a detailed description of winter energy resource utilization by the reindeer population. Reproduction is specified by a modified harmonic mean mating system and the diet choice between different winter energy resources follows the principles of the optimal foraging theory. Wintertime energy intake defines an individual's weight decrease and its consequences on mortality and reproduction. Lichen growth depends on habitat type and lichen biomass. The decision variables are the animals chosen for slaughter from each age and sex class and the amount of supplementary food given. Results show that the availability of arboreal lichens, the growth rate of ground lichens, and pasture rotation all determine the optimal solutions. Reindeer management aiming to maximize long-term net economic revenues leads to very low lichen densities if intensive feeding becomes optimal in the long-term steady state. Government subsidies promote reindeer herders to base management on supplementary feeding leading to lower pasture conditions and to the depletion of lichens.

Estimating ages of white-tailed deer: Age and sex patterns of error using tooth wear-and-replacement and consistency of cementum annuli

The age structure of harvested animals provides the basis for many demographic analyses. Ages of harvested white-tailed deer (Odocoileus virginianus) and other ungulates often are estimated by evaluating replacement and wear patterns of teeth, which is subjective and error-prone. Few previous studies however, examined age- and sex-specific error rates. Counting cementum annuli of incisors is an alternative, more accurate method of estimating age, but factors that influence consistency of cementum annuli counts are poorly known. We estimated age of 1,261 adult (≥1.5 yr old) white-tailed deer harvested in Wisconsin and Illinois (USA; 2005–2008) using both wear-and-replacement and cementum annuli. We compared cementum annuli with wear-and-replacement estimates to assess misclassification rates by sex and age. Wear-and-replacement for estimating ages of white-tailed deer resulted in substantial misclassification compared with cementum annuli. Age classes of females were consistently underestimated, while those of males were underestimated for younger age classes but overestimated for older age classes. Misclassification resulted in an impression of a younger age-structure than actually was the case. Additionally, we obtained paired age-estimates from cementum annuli for 295 deer. Consistency of paired cementum annuli age-estimates decreased with age, was lower in females than males, and decreased as age estimates became less certain. Our results indicated that errors in the wear-and-replacement techniques are substantial and could impact demographic analyses that use age-structure information. © 2014 The Wildlife Society.

Altitudinal variation in body size and age structure of the Sauter’s frog Rana sauteri in Taiwan

The tendency for organisms to be larger in cooler climates, the so-called Bergmann’s rule, has been widely observed in endotherms, but it is debatable in ectothermic anurans. Altitudinal variations in body size, age, and growth rate of the Sauter’s frog Rana sauteri were investigated with skeletochronology at six sites along the altitudinal gradients from 330 to 2,320 m in subtropical Taiwan. The aims of this study were to determine whether these life history traits vary with altitude and differ between males and females. The body size of male R. sauteri followed a converse Bergmann’s cline; the size decreased with increase in altitude, while no significant altitudinal change was found for females. The size dimorphism was female-biased and became greater at higher altitudes because of the altitudinal decrease in male size. Ages ranged between 1 and 5 years for males and 1 and 6 years for females. There was no significant difference in the age structures between the two sexes, but both sexes had higher average ages at higher-altitude sites. According to von Bertalanffy’s model, the growth coefficients decreased with increase in altitude for males but not for females. The annual growth rates were greater for all age classes of females than males, suggesting that growth rate was a major factor underlying body size patterns of both sexes. Growth rate was a major factor underlying body size patterns in both sexes of R. sauteri. It could be affected by not only altitudinal temperature gradient but also sex-biased life history traits and environmental factors.

Bioaccumulation of organochlorine contaminants and ethoxyresorufin‐o‐deethylase activity in southern California round stingrays (Urobatis halleri) exposed to planar aromatic compounds

While contaminant concentrations have been reported for elasmobranchs around the world, no studies have examined bioaccumulation patterns across male and female age classes. The round stingray (Urobatis halleri) is a local benthic species that forages near areas of high organochlorine contamination and represents a good elasmobranch model. Polychlorinated biphenyls (PCBs), DDT, and chlordanes were measured in juvenile and adult male and female stingrays from areas in southern California, USA (n = 208), and a nearby offshore island, Santa Catalina (n = 34). Both mainland juvenile male and female stingrays showed a significant dilution effect. After maturity, summed contaminant concentrations significantly increased with size for adult males (median 11.1 µg/g lipid wt) and females (5.2 µg/g lipid wt). However, the rate of bioaccumulation was substantially greater in male stingrays than in females, likely a result of the females' ability to offload contaminants to offspring during pregnancy. In addition, males and females showed significant differences in their contaminant profiles, suggesting differential habitat use. Male and female stingrays collected from Santa Catalina Island had significantly lower concentrations (0.51 µg/g and 0.66 µg/g lipid wt, respectively), approximately 5 times less than those of mainland animals. Potential toxicity effects mediated through activation of the aryl hydrocarbon receptor were explored through ethoxyresorufin-O-deethylase (EROD) activity assays. Mainland male stingrays exhibited significantly greater EROD activities than Catalina males (481 pmol/min/mg protein and 55 pmol/min/mg protein, respectively); however, activity levels in female stingrays from both locations were comparable (297 pmol/min/mg protein and 234 pmol/min/mg protein, respectively) and lower than those in mainland males. The results suggest that PCBs and/or other structurally related contaminants may be inducing a biological response in mainland males but not females, possibly the result of a dampening effect of estradiol; however, the exact physiological repercussions of exposure remain to be determined.

Restrictive mate choice criteria cause age-specific inbreeding in female black grouse, Tetrao tetrix

Inbreeding is generally rare in large, natural populations yet mate choice often appears to be random with respect to kinship. This suggests that the risks of inbreeding may be small because passive mechanisms of inbreeding avoidance, for example dispersal, are effective at lowering inbreeding risk. Previous theoretical and empirical studies have assumed that the risks of inbreeding are constant over an individual’s life span, but in the lek-breeding black grouse, inbreeding increases with female age. To determine whether inbreeding avoidance mechanisms are also age dependent, we generated four null models of random mate choice ranging from complete randomness to more biologically realistic mate choice criteria and compared these to 8 years of data on inbreeding levels at four different female age classes. We additionally tested whether mate fidelity decreased inbreeding risk. Observed inbreeding in female age classes 1, 2 or <3 were not significantly different from random, but was approximately 3.5 times higher in female age class <4. Alternative models using mate choice criteria showed no significant differences between observed and expected levels for any age class. Our results are in line with previous studies on noncooperatively breeding passerine birds, which indicate that mating is random with respect to kinship and that increased inbreeding in older females can be explained by reduced male availability caused by restrictive mate choice criteria. We also found that individuals that switched mates significantly increased relatedness to partners suggesting that mate fidelity may have evolved as an important passive inbreeding avoidance mechanism.

Size-assortative pairing across three developmental stages in the Zeus bug, Phoreticovelia disparata

The mechanisms underlying size-assortative pairing have received considerable attention. Typically, pairing is assumed to occur at, or just prior to, the adult phase of the life cycle. However, in many invertebrates, males commence associations with juvenile females who are more than a single moult away from sexual maturity. These species are ideal to explore the importance of reproductive and survival benefits as mechanisms driving size-assortative pairing. In the Zeus bug, Phoreticovelia disparata, adult males are found riding on juvenile (fourth and fifth instar) and adult females—a behaviour that is costly for females but has survival benefits for males. Using a combination of field collections and laboratory manipulations, we show that pairing is size-assortative both within and between female age classes and that riding males are smaller than non-riding males. In a series of mating trials, we revealed that males attempt to ride any female but that their riding success is dependent on female age. We also provide the first direct evidence of female resistance to male riding attempts in P. disparata. We propose that size-assortative pairing arises through adaptations that have evolved to minimise the potential costs of sexual conflict. We suggest that the selective pressure on males to maximise survival benefits is sufficiently high that it outweighs the reproductive benefits of discriminating against fourth instar females. Finally, given that female resistance is under direct selection in juvenile females, it is likely to be the main form of selective pressure for adult females.

Managing wild boar - considerations for wild boar management based on game biology data

Keuling O (2009) Managing wild boar Considerations for wild boar management based on game biology data. Doctoral dissertation. Objectives To prevent economic problems by high wild boar populations, an effective and biologically based wild boar management has to be established. A lot of wild boar research has been done in the last decades. However, game managers were not able to incorporate this knowledge into the development of effective management strategies. Thus, furthermore studies have to be accomplished to expand wild boar science and management. This thesis, based on a radiotelemetric study in southwestern Mecklenburg–Western Pomerania, presents research results on wild boar space use patterns, dispersal, grouping patterns and divisions. For all these measures I examined the influence of age classes and environmental factors affecting behavioural patterns (e.g. hunting, seasonal resources, seasonal requirements). Finally, I discussed efficiency and amount of hunting pressure of different hunting methods. Results The wild boar groups divided temporarily in 12.3 % of all observed localisations. We defined four types of divisions: short-term local, short-term extensive, long-term extensive and final division. The small home range sizes did not differ between age classes or group types with a slight tendency for larger home ranges of yearlings, especially in summer. The shift of summer home ranges was stronger in yearlings than in adults. Three space use patterns occurred in summer: field sows, commuters and forest sows. Only 15 % of all shot animals were shot outside their mothers’ home range, only one fourth of these “dispersed” animals were females. Males were shot at larger distances than females. Diurnal activity was positively influenced by daytime length, nutritional needs and fewer disturbances. Due to this reasons an impact of hunting was not clearly detectable. Hunting did influence activity and space use only in moderate intensities. Single hunt from hides is the dominating and an efficient hunting method. The sustainable harvest rate was not exhausted. Conclusions The small home ranges and low, male biased, dispersal rates denote strong site fidelity in all age and reproductive classes within female wild boar. The short distances and low dispersal rates, even within males, might be affected by all year round equably distributed high abundance of resources. Changed space use patterns in summer are mainly influenced by changed food availability. Although hunting was often presumed to be responsible for behavioural changes, little direct influences were observed in this study. The results reflect an interaction between habitat types, season, and nutritional needs on most behavioural patterns. Sound nutritional conditions and year-round low hunting pressure might be responsible for similar seasonal home ranges. Group fluctuations, occurrence of sub-groups as well as temporary and final divisions seem to be common behavioural patterns within wild boar groups, depending on age classes, reproduction, and seasonal nutritional supplies. Wild boar groups react flexible on several seasonal internal and extrinsic factors. The omnivore wild boar is enabled easily to adapt to various environments. Its wide eco-ethological plasticity enables the species to colonize new habitats and enlarge its distribution. All over Europe hunting rates seem to be lower than reproduction of wild boar. To reduce populations and thus, damages, supplemental feeding should be reduced and hunting rates have to be increased especially for females, as all age classes of females are highly reproductive. Hunting management is the most important tool for disease and damage control. As all hunting methods caused similar and negligible disturbances in this study, efficiency should get top priority. The combination of different hunting methods is necessary for reduction on comprehensive areas.

Epidemiologic Survey for Brucella suis Biovar 2 in a Wild Boar (Sus scrofa) Population in Northwest Italy

In 2001, antibodies to Brucella spp. were detected in the wild boar (Sus scrofa) population of Regional Park in the Piedmont, northwest Italy. This was the first report of swine brucellosis in Italian wildlife, and in response, we conducted a survey on wild boars culled in the park to evaluate the presence and epidemiologic pattern of Brucella. In total, 2,267 serum samples and 1,841 tissue samples were collected and tested from 2001 to 2007. Differences in antibody and infection prevalence among sampling years were statistically significant (chi(2)=28.2, P<0.0001 and chi(2)=27.8, P<0.0001, respectively). Serologic and culture results also differed between gender and age groups, and for serology, a positive age trend was observed in both male and female age classes (chi(2(trend))=90.9, P<0.00005 OR: 1, 2.5, 4.9, 7.5; chi(2(trend))=43.1, P<0.00002, OR: 1, 2.5, 2.9, 4.8, respectively).

Apparent Survival of Adult Magnificent Frigatebirds in the Breeding Colony of Isla Isabel, Mexico

Abstract Annual apparent survival rates of the Magnificent Frigatebird (Fregata magnificens) were estimated from 1998 to 2003 using a capture-resight model with 870 marked adult birds on Isla Isabel, Mexico (21°51’N, 105°54’W). The most parsimonious model was a time since marking model (or two age class model) with constant resighting rate for males and females (pm and pf), constant apparent survival rate for males in both age classes (ϕ1m and ϕ2+m), and time-dependent apparent survival rate for females (ϕ1f and ϕ2+f) in both age classes. We found higher resighting rates in males than in females, a tendency of higher apparent survival in females than in males in 1999, a clear higher apparent survival rates in females than in males in 2000, nearest the same apparent survival rates of the two age classes of males throughout, and differences in apparent survival between age classes of females showing considerable annual variation within age classes. The results suggest permanent emigration of females from th...

Survival of Female Northern Pintails Wintering in the Playa Lakes Region of Northwestern Texas

The continental population of northern pintails (Anas acuta; hereafter pintails) has declined since the late 1970s, possibly due to poor breeding propensity, low nest success, and low survival rates in response to habitat loss. Survival estimates are unavailable for several winter and migration areas including the Playa Lakes Region (PLR) of northwestern Texas, USA. We investigated winter survival rates, documented periods of mortality, and identified possible causes of mortality for 159 and 168 radiotagged female pintails during 23 October 2002–18 February 2003 and 10 October 2003–18 February 2004, respectively. We located all radiotagged pintails at least once weekly to verify survival status and used-known fate modeling in program MARK to test the influence of capture period, female age class, body mass, and capture location on survival rates. Cumulative survival for the 119-day period in 2002–2003 was 0.925 (95% CI = 86.0–96.3). During 2003–2004, for a 134-day period, survival estimates declined to 0.694 (95% CI = 57.1–79.5). The period of highest mortality occurred during the pintail hunting season with 88% of deaths during 2002–2003 and 34% of deaths during 2003–2004 occurring during this period. Age class and capture period did not affect survival rates either year. There was a positive linear correlation between body mass at time of capture and survival rates during winter for 2003–2004. The lower survival during 2003–2004 was probably due to fewer wetlands being available in the PLR. Our results suggest that habitat conditions and hunting disturbance impact survival of pintails in the PLR of Texas. To maintain or increase wintering pintail survival in the PLR, management should expand wetland availability to wintering waterfowl, enhance food resources, provide refuging areas, and initiate a means for perpetual conservation of playas.