Body size variation of four latitudinally‐separated populations of a toad species: age and growth rate as the proximate determinants

Age and growth rate are critical parameters determining the body size of adult anurans, which grow indeterminately. Therefore, evaluating their relative importance and selective pressures acting on them may help to explain variation in body size of anurans across geographical populations. Based on the data on body size and skeletochronological age of 4 Asiatic toad (Bufo gargarizans) populations that are widely separated in latitude, the present study showed that toads at the northern extremity of the range were the oldest, on average, and grew relatively fast, toads at the southern end of the range were relatively old but grew fastest, whereas mid‐latitude toads were intermediate in both traits. These results indicated that relative contributions of age and growth rate to body size differed among populations. From a life history perspective, greater age attained by toads at higher latitudes should result from delayed maturation, and faster growth from an adaptive response to strong seasonal time constraints; in contrast, selective pressures on the 2 parameters at lower latitudes might be associated, respectively, with low adult death rates and longer favorable growing seasons.     

Reproductive strategies in males of the world's southernmost lizards

Reproductive and life history patterns in reptiles are tightly related to the environmental conditions, so male reproductive cycles have been historically characterized as continuous, for tropical lizards, or seasonal, for temperate lizards. However, males of Liolaemus and Phymaturus lizards (Liolaemidae), from cold temperate climates of high altitudes or latitudes in Argentina and Chile, have developed a variety of reproductive cycles to coordinate with the short female reproductive season and to deal with the low frequency of reproductive females in the population. Using gonadal histology and morphological analysis, we describe the male reproductive biology, fat storage and sexual dimorphism of the viviparous lizards Liolaemus sarmientoi and Liolaemus magellanicus that inhabit an austral grass steppe at 51°S, in the southern limit of the American continent. Males of L. sarmientoi and L. magellanicus are reproductively available during the entire activity season of approximately 5 months. In addition, males of both species exhibit greater body sizes than females in morphological variables relevant in sexual selection. Meanwhile, females of both species exhibit larger inter‐limb length than conspecific males, which suggests fecundity selection to increase space for a larger litter size. The continuous sperm production throughout the activity season allows these liolaemids to mate at any time when females ovulate, representing a selective advantage to deal with the short activity season and the adversities of the cold environment they inhabit.     

Mojave desert tortoise (Gopherus agassizii) thermal ecology and reproductive success along a rainfall cline

Desert resource environments (e.g. microclimates, food) are tied to limited, highly localized rainfall regimes which generate microgeographic variation in the life histories of inhabitants. Typically, enhanced growth rates, reproduction and survivorship are observed in response to increased resource availability in a variety of desert plants and short‐lived animals. We examined the thermal ecology and reproduction of US federally threatened Mojave desert tortoises (Gopherus agassizii), long‐lived and large‐bodied ectotherms, at opposite ends of a 250‐m elevation‐related rainfall cline within Ivanpah Valley in the eastern Mojave Desert, California, USA. Biophysical operative environments in both the upper‐elevation, “Cima,” and the lower‐elevation, “Pumphouse,” plots corresponded with daily and seasonal patterns of incident solar radiation. Cima received 22% more rainfall and contained greater perennial vegetative cover, which conferred 5°C‐cooler daytime shaded temperatures. In a monitored average rainfall year, Cima tortoises had longer potential activity periods by up to several hours and greater ephemeral forage. Enhanced resource availability in Cima was associated with larger‐bodied females producing larger eggs, while still producing the same number of eggs as Pumphouse females. However, reproductive success was lower in Cima because 90% of eggs were depredated versus 11% in Pumphouse, indicating that predatory interactions produced counter‐gradient variation in reproductive success across the rainfall cline. Land‐use impacts on deserts (e.g. solar energy generation) are increasing rapidly, and conservation strategies designed to protect and recover threatened desert inhabitants, such as desert tortoises, should incorporate these strong ecosystem‐level responses to regional resource variation in assessments of habitat for prospective development and mitigation efforts.     

Geographical variation of mandible size and shape in the Japanese wild pig (Sus scrofa leucomystax)

The mandibles of the Japanese wild pigs (Sus scrofa leucomystax) from various geographical locations, which have been stored in the University of Tokyo and National Science Museum, Tokyo were examined. The mandibles from northern localities were larger in size than those from southern localities. The Oita population was significantly smaller than the Honshu populations. The Mie population was smaller than the Hyogo population in length from the angle of the mandible. In the multivariate analysis, the Kyushu populations could be obviously distinguished from the Honshu populations in the principal component charts. However, each Honshu population did not show the locality-specific distribution of the principal component plots.     

Geographical variation of skull size and shape in various populations in the black giant squirrel

We osteometrically examined the skulls of the black giant squirrel (Ratufa bicolor) from three mainland populations (M. Malayan Peninsula, V. South Vietnam, and B. Burma, India and North Thailand) and from two island populations (T. Tioman, and S. Sumatra Islands). The skull in the Malayan peninsula population was significantly smaller than that of the two other mainland populations. It is consistent with Bergmann's rule as shown in the gray-bellied squirrel. The two island populations did not show obvious differences in comparison with the Malayan population in many measurements. In the proportion analysis eliminating the size factor, the differences among populations were not easily confirmed and we concluded that the osteological characters peculiar to each population could not be shown in this species. The first and second principal component scores of M, S, and T populations were intermingled, whereas the V and B populations of V and B were not separated in the chart. We pointed out that the morphological differences were demonstrated between northern and southern groups of the Isthmus of Kra in the mainland populations, and that the two island populations did not show the island-isolation effect in comparison with the M population. The adaptational variation related to feeding and locomotion could not be confirmed among populations of the black giant squirrel as shown in the proportion analysis.     

Breeding versus survival: proximate causes of abrupt population decline under environmental change in a desert rodent,the midday gerbil (Meriones meridianus)

Studying abrupt ecological shifts under gradual environmental change caused, in particular, by human activity is important for understanding the fundamental aspects and underlying mechanisms of ecological resilience. One of the rare well‐documented examples of an abrupt ecological shift is the delayed step transition of the population of a desert rodent, the midday gerbil (Meriones meridianus), from high‐abundance (1994–2002) to low‐abundance (2003–2017) regimes. This was in response to landscape transformation from desert to steppe caused by the drastic reduction of livestock in the rangelands of southern Russia after the collapse of the USSR in the early 1990s. In this study, we tested whether demographic parameters were correlated with the observed abrupt downward population shift. We found that reproductive activity (the percentage of breeding females, the number of litters, fecundity and the number of young recruited per female) showed no trend over time and did not differ between periods of high and low abundance. In contrast, the adult sex ratio (SR = males: females) decreased significantly with time and was as much as twice more female‐biased for the low‐abundance population regime. However, SR was not related to any reproductive parameter, including the percentage of breeding females. We conclude that proximate reasons for an abrupt population decline in M. meridianus are not associated with the changes in breeding patterns or mate limitation caused by the Allee effect but relate to the increased mortality as a result of the desert landscape being fragmented by steppezation. The mortality is expected to be higher for males as the mobile and dispersing sex.     

Ecology of Wahlberg’s velvet gecko,Homopholis wahlbergii,in southern Africa

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85mmSVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17–19mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significant decrease in testicular activity was in mid-winter (June–August), thus, spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended to eat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance. We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items.     

Climate,female traits and population features as drivers of breeding timing in Mediterranean red deer populations

Understanding the factors that lead to variation in the timing of breeding in widespread species such as red deer (Cervus elaphus) is crucial to predict possible responses of wild populations to different climate scenarios. Here, we sought to further understand the causes of inter‐annual variation in the reproduction timing of female deer in Mediterranean environments. An integrative approach was used to identify the relative importance of individual, population and climate traits in the date of conception of free‐ranging deer, based on a dataset of 829 hinds culled during 12 years. We found that a population trait, density, was the most important factor explaining the variation in conception dates, with greater densities causing later conception dates. Body mass was the second in importance, with heavier females conceiving earlier than lighter ones. Almost equally important was the spring real bioclimatic index, a measure of plant productivity, causing later conception dates in the least productive springs (drier and hotter). Another climatic component, the end of summer drought, showed that the sooner the autumn arrives (greater rainfalls and cooler temperatures) the earlier the conception dates. Interestingly, age class was found to be a minor factor in determining conception date. Only older females (≥10 years old) conceived significantly later, suggesting reproductive senescence. This study highlights not only the importance of population and individual traits but also the influence of climatic parameters on the deer reproductive cycle in Mediterranean environments, giving valuable insight into how reproductive phenology may respond to seasonality and global climate changes.     

Review of the Results of Common Carp (Cyprinus carpio) Breeding at a Large-Scale Hatchery

Long‐term data on the induced spawning of common carp (Cyprinus carpio) at a large‐scale hatchery were evaluated. Breeders at the farm prefer medium‐size fish with body weights between 4 and 8 kg. The number of females selected for propagation in the first period of the spawning season made up about half of the total number of females (47.5%). The average spawning ratio from the data of 2620 females receiving hormonal injections was 79.8%. From the egg production data of 2086 females, the average pseudogonadosomatic index (PGSI) was calculated as 16.3 ± 5.87% (mean ± SD) for the same period. There was a high correlation between fish weight and the time of induction, determined by the breeder on the basis of secondary sexual characteristics. The similarity of the responses of females among the different weight categories proved the reliability of this method for identification. The time of induction has a significant effect on both the responsiveness of the females and the relative quantity of eggs released. Spawning ratio was significantly lower in the third period of the reproductive season, compared with those in the first and second period. Mean PGSIfor the third period was significantly lower than that for the first period. The considerable decrease of both reproductive parameters by the end of the spawning season is attributed to ovarian atresia. The spawning ratio and the mean PGSIfor the mirror and scaled varieties were similar.     

长鬣蜥繁殖生态的研究

2004～2005年,对人工饲养的长鬣蜥繁殖行为和生态习性进行了研究,结果表明：3～7月为长鬣蜥的繁殖期,繁殖行为主要表现为发情求偶、交配和产卵,5～6月为产卵高峰期,每条成熟的雌蜥年产卵2～3窝,平均窝卵数12（7～18）枚;雌蜥每窝产卵间隔33～45 d不等;平均单卵重3.06（2.80～3.50）g;卵径2.63 cm×1.18cm。在自然孵化温度和90%～95%的湿度下孵化期为60～98 d,孵化率52.34%,长鬣蜥幼体初生个体重2.50 g,体全长（头体＋尾）14（4＋10）cm。     

Effect of breeder age and breeding season on egg production and incubation in farmed ostriches

(1) This research was carried out to investigate changes in egg production and hatchability as influenced by age and breeding season of 10 trios (two females, one male) of ostrich (Struthio camellus) during 1998 to 2002. (2) Breeding season affected number of eggs laid per female per season, average egg weight, length of laying period and clutch sequence. (3) The number of eggs laid per female per season was 25 in the first breeding season and 57 by the fifth breeding season. The laying period lasted 169 d in the first season whereas it was 210 d by the fifth season. The breeding season became longer year by year. (4) The number of clutches was two in the first season, three in the second and 4 in the later breeding seasons: the mean interval between cycles was 9 to 10.6 d and the mean number of eggs in one cycle varied from 12 to 14.4. (5) The breeding season affected the hatchability of fertile eggs, chick weight at hatching, hatchability of total eggs, fertility, malpositioned embryos, deformed chicks and assisted chicks during hatching. The first 4 variables increased and the last three decreased, with each breeding season. (6) Weight loss of eggs and length of incubation were unaffected by the breeding season. Hatchability which was 64.3% in the first season increased progressively and reached 73.1% in the fifth breeding season.     

Determinations of the reproductive output of populations of a thalassinid prawn Upogebia africana (Ortmann) in the Swartkops estuary

Populations of large and ‘stunted’ (adult carapace lengths = 17,0–24,0 and 12,0–19,0 mm respectively) Upogebia africana were regularly and quantitatively sampled in the Swartkops estuary. At the site with ‘stunted’ prawns a well-defined spring (July to October) and summer (December to March) breeding cycle was recorded. The ‘stunted’ female prawns produced two broods of eggs per annum and the brood size ranged from about 305 to 2282 eggs depending on the size of the female. At the site with large prawns the spring and summer breeding cycles tended to merge, forming a longer breeding season, with the adult females apparently producing three broods of eggs per annum. The brood size of these females ranged from about 1304 to 4819 eggs. The calculated reproductive output (Pr) and reproductive biomass ratio (Pr/B) of the latter population were much greater than those of the ‘stunted’ prawns (1331 kJ m^?2 y^? and 0,53 v. 332 kJ m^?2 y^?1 and 0,26).     

Female reproductive success in a species with an age‐inversed hierarchy

In most group‐living mammals, reproductive success declines with increasing age and increases with increasing rank. Such effects have mainly been studied in matrilineal and in “age positive” hierarchies, which are stable and in which high ranking females often outperform low ranking ones. These relationships are less well‐understood in age‐inversed dominance hierarchies, in which a female's rank changes over time. We analyzed demographic data of 2 wild, unprovisioned groups of gray langurs (Semnopithecus schistaceus) near Ramnagar, Nepal covering periods of 5 years each. Female rank was unstable and age‐inversed. We measured reproductive success via birth rates (57 births), infant survival (proportion of infants surviving to 2 years) and number of offspring surviving to 2 years of age (successful births) for 3 age and 3 rank classes. We found that old females performed significantly worse than expected (birth rate P = 0.04; successful births P = 0.03). The same was true for low ranking females (P = 0.04, and P < 0.01, respectively). Infant survival was highest for young and middle‐aged as well as for high and middle ranking females. Overall, the results for these unstable hierarchies were rather similar to those for stable hierarchies of other mammals, particularly several nonhuman primates. Compared to a provisioned population of a closely related species, the wild and unprovisioned population examined (i) showed stronger age effects, while (ii) female reproductive success was equally affected by rank. Future comparative studies are needed to examine whether captive or provisioned populations deviate predictably from wild populations.     

A comparison of reproductive parameters of female Amur tigers (Panthera tigris altaica) in the wild and captivity

A healthy population of captive Amur tigers might assist recovery of the wild population in Northeast China if individuals were properly prepared and considered suitable for release in the wild. We analyzed the breeding records of 68 female Amur tigers from 1995 to 2010 in the Hengdaohezi Felid Breeding Center of China and compared the reproductive parameters of this population to wild female Amur tigers. We found that the reproductive parameters of the captive population (the age of first parturition, length of gestation and litter survival rate) were not significantly different from those of wild Amur tigers. Differences in birth date and litter size between wild and captive populations may be caused by management protocols for the captive population or insufficient field data from the wild population. Reproductive parameters of females giving birth after losing a litter were similar to parameters of females that did not lose a litter, except for birth date. These results provide no indication of major problems in using captive females for a breeding program for release of cubs into the wild, but additional information is still needed to assess their suitability.     

矮小型褐壳蛋鸡产蛋时间和间隔的统计分析

本文对８８０只纯系矮小型褐壳蛋鸡的产蛋时间进行了连续５天的观察,分析结果表明,矮小型褐壳蛋鸡的产蛋时间集中在上午１２时以前,并以９：００～１０：００期间产蛋最为密集,占全天产蛋的１９．５％。连产内第一枚蛋产出时间集中在上午（８９：３３％）,以７：００～９：００间产蛋最多（４９．７１％）;而最后一枚蛋产出时间集中在下午（７１．２０％）,以２：００～４：００间产蛋最多（３６．５８％）。矮小型褐壳蛋鸡连产内产蛋间隔范围为２２．３５～３１．１５小时,每枚蛋平均间隔高峰在２４小时（３６．０％）,群体平均产蛋间隔为２５．０８小时。相邻连产间间隔时间的变异范围很大,最短为３８．０小时,最长达１００．４５小时。     

Regional variations in the nematode worm populations of breeding ewes in New Zealand

AIM: To determine whether the generic composition of nematode parasites in lactating ewes varies between geographic regions in New Zealand and whether age and fecundity of ewes affect nematode egg output. METHODS: Four ram breeding properties in each of the northern (NNI) and southern (SNI) North Island and the northern South Island (NSI) regions, together with six properties in the southern South Island (SSI) were investigated. Faecal samples were obtained on one occasion, 2-6 weeks after lambing, from at least 60 ewes on each property, stratified according to age and reproductive status. Nematode eggs were counted and coprocultures prepared to identify genera present. Information on the history of anthelmintic use on each property was also collected. RESULTS: Highest faecal egg counts (FEC) were observed from ewes in the NNI and SSI regions. Lambed hoggets and twin-rearing two-tooth ewes had higher FEC than their unlambed or single-lamb-rearing contemporaries, respectively. However, no significant effect of reproductive effort on FEC was demonstrated in mixed-aged ewes. Significant regional differences in generic composition of nematode parasites were observed: Teladorsagia spp (also referred to as Ostertagia spp) eggs made up 56% of total eggs shed from sheep in the SSI compared with14% in the NNI, and values for Haemonchus spp were 1%and 24% for these same regions, respectively. Trichostrongylus colubriformis and T. vitrinus together made up 7, 15, 13 and15% of eggs counted from sheep in the SSI, NSI, SNI and NNI, respectively. CONCLUSIONS: More comprehensive epidemiological information may suggest regional-specific approaches to the management of nematode parasites in ewes should be devised in the future.     

高原鼢鼠种群消长与繁殖特性的关系

通过对高原鼢鼠３个具有不同栖息史的种群连续３年的观测,研究了种群数量消长与种群性比、怀胎率、胎仔数、繁殖强度间的对应关系。结果表明,高原鼢鼠在某一适生地栖息时间的长短对其种群数量的稳定具有决定性影响,即栖息史越长,种群稳定性越好;种群性比在１．０左右时,表明种群数量呈上升之势,在１．３左右时,种群数量处于相对稳定状态,大于１．５时,种群数量将趋于减少;种群中雄性个体的数量和比例与怀胎率、胎仔数和繁殖强度呈正相关,因而它的变化在一定程度上决定着种群数量的消长。     

Geographical variation of the skull morphology of the common tree shrew (Tupaia glis).

Geographical variation was examined morphologically in the common tree shrew (Tupaia glis) in some Indochinese and Malayan regions. Osteometrical examination and principal component analysis elucidated the morphological differences among various populations. The populations from southern and western Thailand were distinguished morphologically from the other populations. Variation in males from south Thailand and Kuala Lumpur suggests that the Isthmus of Kra may have an influence on the variation of skull morphology. However, the Isthmus of Kra was not completely considered as a factor of geographical separation in this species, because we could not confirm the separation in skull size and shape between the localities at least in females. While, the Kanchanaburi population in western Thailand was significantly smaller than the other population in skull size, and constituted the morphologically separable group in our study.     

Does multiple seed loading in Blue Jays result in selective dispersal of smaller acorns?

Studies from both tropical and temperate systems show that scatter‐hoarding rodents selectively disperse larger seeds farther from their source than smaller seeds, potentially increasing seedling establishment in larger‐seeded plants. Size‐biased dispersal is evident in many oaks (Quercus) and is true both across and within species. Here, we predict that intraspecifc variation in seed size also influences acorn dispersal by the Blue Jay (Cyanocitta cristata Linnaeus), but in an opposite manner. Blue Jays are gape‐limited and selectively disperse smaller acorn species (e.g. pin oaks [Quercus palustris Münchh]), but often carry several acorns in their crop during a single dispersal event. We predict that jays foraging on smaller acorns will load more seeds per trip and disperse seeds to greater distances than when single acorns are carried in the bill. To test this, we presented free‐ranging Blue Jays with pin oak acorns of different sizes over a 2‐year period. In each of 16 experimental trials, we monitored the birds at a feeding station with remote cameras and determined the number of acorns removed and the distance acorns were dispersed when cached. Jays were significantly more likely to engage in multiple seed loading with smaller seeds in both years of the study. During the second year, these smaller acorns were dispersed farther than larger acorns, and during the first year, larger acorns were dispersed farther, revealing an inconsistent response to seed size during our study. We suggest that in some circumstances, multiple seed loading by Blue Jays may favor dispersal in some plant species.     

The Female Reproductive Cycle of the Neotropical Snake Atractus pantostictus (Fernandes and Puorto, 1993) from South‐eastern Brazil

Data on reproductive activity of fossorial species are limited because the specimens are difficult to be observed and captured. Here in, we present the reproductive cycle of female Atractus pantostictus, a fossorial neotropical species, and the sexual maturity of males and females in south‐eastern Brazil. The female reproductive cycle of A. pantostictus is seasonal, with vitellogenic follicles being found from September to April and eggs in November, February, March and April with the number varying between two and four. Spermatozoa were found in the lumen of the glandular and non‐glandular uterus in females collected during the rainy season. Sperm storage tubules were found in the posterior infundibulum of the females, where the storage of sperm occurs for a short time. The storage may occur because mating and ovulation are dissociated.