Mean Annual Fecundity Research Articles

Age-specific, population-level pedigree of wild black bears provides insights into reproduction, paternity, and maternal effects on offspring apparent survival.

Wildlife pedigrees provide insights into ecological and evolutionary processes. DNA obtained from noninvasively collected hair is often used to determine individual identities for pedigrees and other genetic analyses. However, detection rates associated with some noninvasive DNA studies can be relatively low, and genetic data do not provide information on individual birth year. Supplementing hair DNA stations with video cameras should increase the individual detection rate, assuming accurate identification of individuals via video data. Video data can also provide birth year information for individuals captured as young of the year, which can enrich population‐level pedigrees. We placed video cameras at hair stations and combined genetic and video data to reconstruct an age‐specific, population‐level pedigree of wild black bears during 2010–2020. Combining individual birth year with mother–offspring relatedness, we also estimated litter size, interlitter interval, primiparity, and fecundity. We used the Cormack‐Jolly‐Seber model in Program Mark to evaluate the effect of maternal identity on offspring apparent survival. We compared model rankings of apparent survival and parameter estimates based on combined genetic and video data with those based on only genetic data. We observed 42 mother–offspring relationships. Of these, 21 (50%) would not have been detected had we used hair DNA alone. Moreover, video data allowed for the cub and yearling age classes to be determined. Mean annual fecundity was 0.42 (95% CI: 0.27, 0.56). Maternal identity influenced offspring apparent survival, where offspring of one mother experienced significantly lower apparent survival (0.39; SE = 0.15) than that of offspring of four other mothers (0.89–1.00; SE = 0.00–0.06). We video‐documented cub abandonment by the mother whose offspring experienced low apparent survival, indicating individual behaviors (e.g., maternal care) may scale up to affect population‐level parameters (e.g., cub survival). Our findings provide insights into evolutionary processes and are broadly relevant to wildlife ecology and conservation.

Demography of a stable population of Crab Plovers wintering in Oman

The monotypic Crab Plover Dromas ardeola winters around the shores of the Indian Ocean and breeds in colonies on islands around the Arabian Peninsula. The IUCN lists the world population of Crab Plovers as stable, but long-term survey data or demographic estimates regarding the species status are lacking. Here, we use survey and demographic data collected from 2011 to 2015 to study the status of the population of Crab Plover at their most important wintering area: the Barr Al Hikman Peninsula in the Sultanate of Oman. Our survey data showed that the population of Crab Plovers initially increased and then stabilized. The overall observed finite rate of population change ( $$\bar{\lambda }_{\text{obs}}$$ ) was estimated at 1.004 (0.995–1.013 95% Bayesian credible interval [BCI]), indicating a stable population (7000–9000 birds), that is possibly at carrying capacity. Based on mark-recapture data, the mean annual apparent survival probability of Crab Plovers was estimated to be 0.90 (0.85–0.94 95% BCI). We used counts of adults and yearlings to estimate the mean annual fecundity rate at 0.06 young per pair. Using these demographic values, the overall mean expected finite rate of population change ( $$\bar{\lambda }_{ \exp }$$ ) was estimated to be 0.949 (0.899–0.996 95% BCI), so there is a low chance that $$\bar{\lambda }_{\text{obs}}$$ and $$\bar{\lambda }_{ \exp }$$ overlap. $$\bar{\lambda }_{\text{obs}}$$ and $$\bar{\lambda }_{ \exp }$$ would completely match if about 450 Crab Plovers immigrate to Barr Al Hikman each year. Regional surveys show that yearling densities are higher closer to the breeding areas, so immigrants could be birds that during their first winter stayed close to their natal area. Our study support the IUCN listing of Crab Plover as stable, but further population-wide monitoring is required. From a conservation point of view it is important to continue monitoring because Crab Plovers breed and winter in a region that is rapidly developing.

Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia

Context Understanding population dynamics of invasive species is crucial for the development of management strategies. Feral horses (Equus caballus) are a growing problem in the Tuan–Toolara State Forest (TTSF), a coniferous plantation in south-eastern Queensland, Australia. Aim The population dynamics of the TTSF feral horses was not known. Therefore, the study was designed to characterise the major vital parameters of this population and, using these data, develop a long-term management plan. Methods The study was conducted over 3 years (2011–14) involving 522 individually identified horses. Foaling rates were used to calculate fecundity. Body fat distribution was estimated using body condition score (BCS), which reflects the nutritional, metabolic and general health of individual animals. Multi state mark–capture population models were used to estimate age-specific survival, and the Leslie age-structured projection matrix model was used to determine the annual rate at which the population increased. Key results The mean annual fecundity was low (0.23 ± 0.07 s.d.). The mean BCS of the population was mid-range (2.55 ± 0.51 s.d.) with adult females having lower scores than other age and gender groups. Survival estimates were consistently high (0.92–0.95) across all age groups. The average annual finite rate of population increase (λ) for the 3 years of the study was 1.09. Sensitivity analysis demonstrated that the population growth rate was almost seven times more sensitive to changes in adult survival compared with juvenile survival, and almost twice as sensitive to changes in fecundity. Key conclusions Population dynamics of the TTSF feral horses were comparable to other feral horse populations similarly challenged by environmental nutritional limitations. Implications Defining population dynamics of the TTSF feral horses permits the formulation of management goals that can be audited and adapted as required. The most effective strategy for controlling population growth in the TTSF would involve the continuing removal of substantial numbers of adult females or manipulation of survival and/or fecundity. As selective removal will likely alter the adult sex ratio and age structure of the population, ongoing assessment is necessary to minimise adverse welfare outcomes.

The use of uterine scars to explore fecundity levels in invasive alien tree squirrels

In invasion ecology, reliable measures of female fecundity are necessary to infer population growth rate and develop control programs to determine the proportion of animals that should be culled to reduce population size. Here, we present a reliable staining technique of uterine scars to determine individual fecundity in terms of both seasonal and total (annual) number of young born per female. We applied this method to two alien squirrels species (grey squirrel, Sciurus carolinensis and Pallas’s squirrel, Callosciurus erythraeus ) introduced in Northern Italy, obtaining carcasses from control campaigns from 2011 to 2013. We also investigated environmental and phenotypic variables that might affect individual variation in fecundity and compared annual reproductive output between the two species. For grey squirrels (n=44), 25% of examined females produced a single litter and 61% two litters. Females which reproduced in both seasons tended to have larger summer than spring litters (on average 2.61 and 1.94 offspring, respectively) and mean annual fecundity was 3.4 scars/female ranging from 1 to 8 births. There was no effect of year, eye lens weight, body size or body mass on total fecundity. For Pallas’s squirrel (n=31), 58% of females had a spring litter, some of these also produced a summer litter (35%) and a few even a third litter in autumn (10%). Heavier and older females (higher eye lens weight) had more uterine scars than younger animals with lower body mass. Finally, fecundity of the two IAS in Italy was similar or even higher than in the native range and/or in other countries of introduction, suggesting they are well adapted to their new environment and potentially have a high capacity to spread and recover after reduction of population size. Download the complete issue.

Life history traits associated with low annual fecundity in a central African Parid: the Stripe-breasted Tit Parus fasciiventer

Most Parus species live in the tropics or sub-tropics, and are likely to show life history traits associated with relatively high survival and low fecundity. Based on a 15-year study, we provide the first detailed account of the life history traits of an equatorial Parid, the Stripe-breasted Tit P. fasciiventer, which we contrast with published accounts of north temperate races of the Great Tit P. major. Stripe-breasted Tits fledged a mean of just 1.62 offspring clutch−1, but laid up to four clutches year−1 (mean 1.72) over 11 calendar months, raising their mean annual fecundity to 3.09 fledglings female−1, less than half that of European Great Tits but double that of single-brooded southern African congeners. During incubation, Stripe-breasted and Great Tit females showed similar levels of nest attentiveness, spending 84 and 83–86 % of each 24-h period on the nest, respectively. In contrast, Stripe-breasted Tit parents provisioned at just 10–18 % of the rates recorded for European Great Tits, suggesting that parental investment or prey availability in their respective habitats differed to a similar degree. Consequently, Stripe-breasted Tit nestlings grew more slowly, remained in the nest 4.6 days (20 %) longer, but fledged with proportionately longer wings, perhaps improving their ability to avoid predation. Offspring were last recorded receiving parental care at a mean of 81 days post-fledging (four times longer than is typical of European Great Tits) and remained with their parents for up to 3 years. Helpers were recorded at 61 % of Stripe-breasted Tit nests, and 76 % of breeding adults had helpers during at least one breeding attempt. While latitudinal comparisons often focus on clutch size, much greater disparities were thus evident in other traits, including brood provisioning, the duration of post-fledging care and the incidence of cooperative breeding.

Reproductive biology of the lesser guitarfish Zapteryx brevirostris from the south-western Atlantic Ocean

This study provides the first detailed information on the reproductive biology of the lesser guitarfish Zapteryx brevirostris in the south-western Atlantic Ocean between latitudes 34° and 42° S. A total of 320 males (196-647 mm total length, L(T)) and 336 females (200-640 mm L(T)) were analysed. No significant differences were observed in size at 50% maturity between males (499 mm L(T)) and females (506 mm L(T)). Three seasonal patterns were related to the testes mass, the development of spermatocysts and the presence of spermatozoa in genital ducts. Females showed a 3 year reproductive cycle, with 2 years of ovarian maturation and 1 year of gestation, including a mean annual fecundity of one to two embryos. Synchronicity of both ovulating females and males with sperm in genital ducts indicated that ovulation and hence mating occurs during winter. Birth was assumed to occur during winter, but neither ovulation nor mating is simultaneous with this reproductive event. Despite its low economic value, a decline in abundance in the region, together with a low reproductive efficiency, indicates that the Z. brevirostris population should be monitored closely.

Natural Mortality Rates during Life History Stages of the Red Grouper on Campeche Bank, Mexico

AbstractThe objective of this study was to arrive at biologically convincing estimates of the natural mortality rate (M) for different life history stages of the red grouper Epinephelus morio on Campeche Bank, Mexico. Estimates of M must be compatible with our knowledge of life histories and are essential as input to analytical assessment models for any exploited stock. Because of difficulties in estimating M directly, M has often been incorrectly assumed to be constant with age for a fishery harvesting different age‐groups. The gnomonic interval method (GIM) was applied to this long‐lived species to estimate a vector of M‐values for successive life history stages. The GIM estimates the vector of M at age from the duration of successive development stages and the mean annual fecundity. Estimates were calibrated using available independent data. We computed the relationship between M and age (t) over a 13‐year period as M t = 0.8976t−0.93. Values of M estimated by GIM for adult red grouper were not significantly different (P > 0.05) from those reported in the literature.

Reproductive Ecology and Cub Survival of Florida Black Bears

Abstract: We investigated reproductive ecology and cub survival of Florida black bears (Ursus americanus floridanus) in Ocala National Forest and the adjacent residential area of Lynne, Florida, USA, 1999‐2003. We documented production of 81 cubs from 39 litters. Average litter size was 2.08 ± 0.11 (SE) cubs. The mean age of first reproduction was 3.25 ± 0.27 years. Excluding females that reproduced in consecutive years due to litter loss, interlitter interval was 2.11 ± 0.11 years. The mean annual fecundity rate was 0.57 ± 0.06. We used expandable radiocollars to monitor the fate of 41 bear cubs. The probability of cubs surviving to 9 months of age was 0.46 ± 0.09 and did not differ between cohorts or study locations. The most important causes of cub mortality included infanticide and mortality caused directly or indirectly by collisions with vehicles. Our results indicate that reproductive rates of female black bears in the Ocala study area are comparable to those reported for other black bear populations from eastern United States, but cub survival rates are lower than those reported for most black bear populations. Management of Florida black bears should emphasize strategies to reduce the mortality of cubs.

Population-Specific Demographic Estimates Provide Insights into Declines of Lark Buntings (Calamospiza Melanocorys)

Abstract Many North American prairie bird populations have recently declined, and the causes of these declines remain largely unknown. To determine whether population limitation occurs during breeding, we evaluated the stability of a population of prairie birds using population-specific values for fecundity and postfledging survival. During 2001-2003, we radiomarked 67 female Lark Buntings (Calamospiza melanocorys) to determine annual fecundity and evaluate contributing factors such as nest survival and breeding response (number of breeding attempts and dispersal). Collectively, 67 females built 112 nests (1.67 ± 0.07 nests female−1 season−1; range: 1–3); 34 were second nests and 11 were third nests. Daily nest survival estimates were similar for initial and later nests with overall nest survival (DSR19) of 30.7% and 31.7%, respectively. Nest predation was the most common cause of failure (92%). Capture and radiomarking of females did not affect nest survival. Lark Bunting dispersal probabilities increased among females that fledged young from initial nests and females that lost their original nests late in the season. Conservative and liberal estimates of mean annual fecundity were 0.96 ±0.11 and 1.24 ± 0.09 female offspring per female, respectively. Given the fecundity and juvenile-survival estimates for this population, annual adult survival values of 71–77% are necessary to achieve a stable population. Because adult survival of prairie passerines ranges between 55% and 65%, this study area may not be capable of sustaining a stable population in the absence of immigration. We contrast our population assessment with one that assumes indirect values of fecundity and juvenile survival. To elucidate limiting factors, estimation of population-specific demographic parameters is desirable. We present an approach for selecting species and areas for evaluation of population stability. Las Estimaciones Demográficas Poblacionales Específicas Brindan Pistas sobre la Disminución de Calamospiza melanocorys

Natural mortality and life history stage duration of Pacific sardine (Sardinops caeruleus) based on gnomonic time divisions

The gnomonic-interval natural-mortality method (GIM) that provides an indicative vector of natural mortality (M) of short-lived species was used for species with longevity greater than an annual life cycle. The GIM was solved for the Pacific sardine (Sardinops caeruleus) from the Gulf of California, Mexico. New features added to the original GIM were (a) the use of estimates of the mean annual fecundity, (b) the ability to incorporate observed data for specific interval of durations for developmental stages to calibrate calculations of M vectors, and (c) uncertainty because of fecundity variation. When this approach was used for the Pacific sardine, we did not find statistical differences (P > 0.05) between the GIM estimates and independent estimates based on the literature. The GIM showed that it provides reasonable estimations for the duration of life history stages. Variability in egg-stage duration was also explored for M vectors. We observed daily survival increases as the duration of early stages decrease.

Factors influencing fecundity in migratory songbirds: is nest predation the most important?

Nest predation often is reported to be the major cause of nest failure in birds and by extension the predominant influence on annual fecundity. However, other factors such as the ability of some individuals to renest after a failed nest or to lay additional clutches after successful ones, both of which may in turn be influenced by food availability, can also contribute to individual fecundity. We evaluated the relative importance of nest predation, multiple brooding, renesting, and food availability on mean annual fecundity of a migratory songbird population, using AICc from multiple regression models. In a 16‐yr study of black‐throated blue warblers Dendroica caerulescens, these four variables combined explained 87% of the annual variance in fecundity. Individually, however, food abundance explained more of the variability (35%) than did predation (29%), double‐brooding (19%), or renesting (15%). These results suggest that measuring food availability may be essential to understanding annual differences in reproductive output. They also demonstrate that failing to account for the contribution of food availability, renesting, and multiple brooding in studies of avian demography can result in serious underestimates of mean annual fecundity, potentially biasing calculations of population growth rate, source‐sink dynamics, habitat quality, or population viability.

Temporal Variation in the Vital Rates of an Insular Population of Spotted Owls (Strix Occidentalis Occidentalis): Contrasting Effects of Weather

Abstract We studied the demography of an insular California Spotted Owl (Strix occidentalis occidentalis) population in southern California for 12 years. We used model selection based on information theory to examine the relationship between weather and reproduction and survival. Mean annual fecundity was 0.139 (SE = 0.050) for subadult females and 0.345 (SE = 0.028) for adult females. Adult females had higher fecundity than subadult females during all years, and fecundity in both age classes was higher when a wet year preceded a dry spring (i.e. breeding season). A model incorporating these factors explained 100% of the estimated temporal process variation in fecundity. Mean apparent survival was 0.796 (SE = 0.012), 0.880 (SE = 0.041), 0.692 (SE = 0.062), and 0.368 (SE = 0.038) for adult, second-year subadult, first-year subadult, and juvenile (first-year) owls, respectively. We found no temporal process variation in survival. Using a Leslie projection matrix, we estimated the finite rate of population change to be 0.906 (SE = 0.018) over the entire period of study (1987–1998), which indicated that the population declined ≈9% per year during the study. That rate of decline was higher than a rate (λ1991–1998 = 0.921, SE = 0.020) we estimated for a shorter period (1991–1998) that matched the time interval used in a recent meta-analysis of Spotted Owl population dynamics. We believe that both the present estimates and those of the meta-analysis are valid, given their respective goals. The study population was characterized by relatively high, constant survival of territorial birds, low and variable annual reproduction, and relatively low juvenile survival. Because weather was strongly correlated with reproduction, fecundity rates for the species may decline during short-term droughts and when storms occur during the breeding season. Weather extremes may not, however, be sufficient to affect temporal variation in survival of Spotted Owls in this part of their range.

TEMPORAL VARIATION IN THE VITAL RATES OF AN INSULAR POPULATION OF SPOTTED OWLS (STRIX OCCIDENTALIS OCCIDENTALIS): CONTRASTING EFFECTS OF WEATHER

Abstract We studied the demography of an insular California Spotted Owl (Strix occidentalis occidentalis) population in southern California for 12 years. We used model selection based on information theory to examine the relationship between weather and reproduction and survival. Mean annual fecundity was 0.139 (SE = 0.050) for subadult females and 0.345 (SE = 0.028) for adult females. Adult females had higher fecundity than subadult females during all years, and fecundity in both age classes was higher when a wet year preceded a dry spring (i.e. breeding season). A model incorporating these factors explained 100% of the estimated temporal process variation in fecundity. Mean apparent survival was 0.796 (SE = 0.012), 0.880 (SE = 0.041), 0.692 (SE = 0.062), and 0.368 (SE = 0.038) for adult, second-year subadult, first-year subadult, and juvenile (first-year) owls, respectively. We found no temporal process variation in survival. Using a Leslie projection matrix, we estimated the finite rate of population c...

Variation in fecundity and other reproductive traits in freshwater mussels

Summary1. Life histories of the highly diverse and endangered North American freshwater mussel fauna are poorly known. We investigated reproductive traits of eight riverine mussel species in Alabama and Mississippi, U.S.A.: Amblema plicata, Elliptio arca, Fusconaia cerina, Lampsilis ornata, Obliquaria reflexa, Pleurobema decisum, Quadrula asperata and Q. pustulosa, and compare our results with existing life history information for other species.2. These eight species had reproductive traits characteristic of large, outcrossing populations: hermaphrodites were rare, we found no evidence of protandry, and sex ratios were even or slightly male‐biased.3. Age at sexual maturity varied among species, ranging from <1 to 2 years for L. ornata to 3–9 years for Q. asperata. In all species, most mature females participated in reproduction and fertilisation success was high.5. Fecundity was related positively to both length and age, but length was the best predictor. In six species, fecundity increased exponentially with increasing size; in two species the rate of increase in fecundity declined in larger animals. In four species, fecundity declined in older animals. These latter results indicate weak reproductive senescence; however, in all species, older individuals continued to produce large numbers of offspring. Mean annual fecundity differed widely among species ranging from 9647 to 325 709. Within‐species differences in fecundity were found among rivers and among populations within a river.6. The wide variation in reproductive traits among species indicates the existence of widely divergent life history strategies in freshwater mussels.

Application of Life-History Theory and Population Model Analysis to Turtle Conservation

As more reptiles find their way onto endangered species lists, it is increasingly important to identify management alternatives that can be applied across taxa. I have compared life tables from several turtle populations using elasticity analysis, a method that calculates the proportional contribution of each vital rate (age-specific survival and fecundity) to the annual population multiplication rate, k [In (X) = r, the intrinsic rate of increase]. Most freshwater turtles share similar elasticity patterns across age classes, in spite of large variations in mean annual fecundity, annual survival, and age at maturity. High adult survival elasticity and low fecundity elasticity in these species suggests that conservation efforts that reduce mortality of adults are likely to stabilize declining populations. Desert tortoises and sea turtles had different elasticity patterns, with relatively higher juvenile elasticities when summed across age classes. Three different life tables for painted turtles also showed variation in elasticity patterns. Approximate elasticities can be generated for age-based matrices without a complete life table for each species, requiring only age at maturity, adult female annual survival, and population multiplication rate. This approximation may help identify sensitive life stages for poorly known species, thereby guiding research and management efforts and furthering our understanding of lifehistory patterns.

OBSERVATIONS ON THE FECUNDITY OF HYSSOPUS THYMUS (HYMENOPTERA: EULOPHIDAE)

AbstractThe fecundity of Hyssopus thymus Girault females does not normally vary between generations within a single year, but differences frequently occur between years. A weighted mean annual fecundity of 14 eggs per female under laboratory conditions has been determined by pooling several years’ records, although the maximum number of eggs laid by a female was 130. A mean of 20 eggs per female was determined under quasinatural conditions. The weight of the host, Rhyacionia buoliana (Schiffermüller) (Lepidoptera: Olethreutidae), limits the number of eggs laid per host during the early spring when shoot moth larvae are small. When the host larvae are larger, size is no longer a limiting factor in the number of eggs deposited per host. There is a preoviposition period of about 3 days and egg production is synovigenic. The number of fully developed eggs within a female at one time varies between about 7 and 12 eggs on a 3-day cycle, and never exceeds 16. Each female wasp attacks two or three large host larvae and this number is probably doubled when the host larvae available for attack are small.

The Annual Activity Pattern and Life Cycle of Pterostichus madidus (F.) (Col. Carabidae)

AbstractPitfall trapping, dissections and laboratory rearing of Pterostichus madidus (F.) between I967 and I972 in north east England showed that the annual activity pattern of the species consists of four sections: (i) early summer activity of over-wintered, mostly female beetles; (ii) mid summer activity of newly emerged beetles of both sexes; (iii) late summer activity of maturing, mostly male beetles; (iv) autumn activity of mature and spent, mainly female beetles. Eggs were laid from August until November, with a peak at the end of August. The highest individual fecundity was 80 eggs, but many females laid few or no eggs, partly because of parasitism by Mermis nigrescens Dujardin (Nematoda). Fecundity was normally distributed among females laying ten or more eggs: the mean annual fecundity of these females varied from 20 to 44 eggs per female. Most females died in the autumn, but about a quarter of the female population probably survive the winter, and mature again in the following summer. Larvae developed throughout the winter, reaching the third instar by the spring: this stage has a partial diapause, which delays development at constant temperatures.