Differences In Reproductive Rates Research Articles

Lower Reproductive Rate and Lamb Survival Contribute to Lower Lamb Marking Rate in Maiden Ewes Compared to Multiparous Ewes.

Simple SummaryThe reproductive performance of ewes in their first breeding season (maiden ewes) can be poorer and more variable than at subsequent breeding seasons. However, the extent and causes of the poorer reproductive performance of maiden ewes on Australian sheep farms are not well understood. We used a survey of Australian sheep farmers to compare the reproductive performance of maiden ewes in their first breeding season to multiparous ewes (ewes that have been bred two or more times) on the same farms. We found that the difference in lamb marking rate between non-Merino ewe lambs and multiparous ewes on the same farm was 58%, and for maiden Merino two-tooth ewes, the difference in marking rate compared to multiparous ewes was 22% lower. Poorer reproduction in maiden ewes was due to a combination of poorer reproductive success to mid-pregnancy (reproductive rate), plus poorer survival of lambs between mid-pregnancy and lamb marking. Reproductive performance for maiden Merino two-tooth ewes was correlated with multiparous ewes on the same farm, whereas the reproductive performance of non-Merino ewe lambs was more variable and not associated with the reproductive performance of their multiparous counterparts. The reproductive efficiency of maiden ewes could be improved by addressing factors that improve the reproductive rate and lamb survival between scanning and lamb marking.Suboptimal reproductive performance of maiden (primiparous) ewes remains a source of inefficiency for the Australian sheep industry. However, the extent and causes of the poorer reproductive performance of maiden ewes on Australian sheep farms are not well understood. Here, we show the reproductive performance of maiden ewes relative to their multiparous counterparts on the same farms across Australia using a cohort survey. The difference in marking rate for non-Merino maiden ewe lambs compared to multiparous ewes was 58% (74 vs. 132%; p < 0.001), and this was attributable to a 50% difference in reproductive rate (109 vs. 159%; p < 0.001) and 16% difference in lamb survival to marking (67 vs. 83%; p < 0.001). The difference in marking rate for maiden Merino two-tooth ewes lambing at approximately 2 years-of-age compared to mature multiparous ewes was 22% (80 vs. 102%; p < 0.001) and this was attributable to a 24% difference in reproductive rate (108 vs. 132%; p < 0.001) and 3% difference for lamb survival (75 vs. 78%; p < 0.05). Positive correlations for reproduction traits (reproductive rate, lamb survival and marking rate) between maidens and multiparous ewes were observed for maiden Merino two-tooth ewes (p < 0.001), but these correlations were weak or non-existent for non-Merino ewe lambs. Strategies to improve both reproductive rate and lamb survival can address the poorer and more variable reproductive performance of maiden ewes.

Reproduction probabilities and size distributions of the smooth snake Coronella austriaca in the Netherlands and Norway

Abstract Whether females participate in reproduction every year or rather skip years is pivotal information for understanding the dynamics of animal populations. In ectotherms this reproduction frequency might depend on factors like temperature, individual size, and prey availability. Here we studied the reproduction rate of the smooth snake Coronella austriaca at two latitudes: in Norway and The Netherlands. Reproductive and morphological data were collected in Norway (34 years) and The Netherlands (5 years). To account for differential resighting probabilities of pregnant and non-pregnant females, we performed multi-state mark-recapture analyses. Reproductive rate, quantified as the probability of participating in reproduction in consecutive years, was calculated for both pregnant and non-pregnant females. The results showed a clear difference in reproductive rate between the two latitudes, with only 15% of pregnant females reproducing again in the following year in Norway versus 93% in The Netherlands. Furthermore, in Norway females grew larger and started reproduction at a higher age. Litter size and juvenile total length and body mass were also significantly higher in Norwegian smooth snakes.

Reproductive constraints in frugivorous phyllostomid bats: seasonal and elevational variation in reproductive rates in the Brazilian Atlantic Forest

Reproductive rates in bats are higher when there is a greater availability of food, and when temperatures and rainfall are higher. Along elevational gradients, variation in these factors occurs over a small area, making them ideal natural laboratories for studies that aim to describe reproductive patterns and to identify possible vertical migrations for reproduction. We characterized the seasonal and elevational variation in reproductive rates of female and male Artibeus spp., Carollia perspicillata, and Sturnira lilium in the Brazilian Atlantic Forest. We sampled bats with mist nets at 13 sites in southeastern Brazil, between 23° and 24° of latitude, at elevations between 60 and 1,800 m a.s.l. The reproductive patterns of Artibeus spp. and S. lilium were seasonal, with higher reproductive rates in the period with higher rainfall, temperatures, and, consequently, greater availability of food. Moreover, elevation influenced reproductive activity in all study species. Reproductive rates for females of Artibeus spp. were higher at intermediate elevations (between 501 and 1,000 m a.s.l.), and for females of S. lilium at high elevations (above 1,000 m a.s.l.) with a less evident peak at intermediate elevations. Similarly, the proportions of reproductively active male Artibeus spp. and S. lilium were greater at intermediate and high elevations, respectively. In the dry season, reproductive rates of all females increased with local abundance of all females. Differences in reproductive rates along elevational gradients could influence population dynamics, and therefore entire elevational ranges should be protected to ensure conservation of the best reproductive habitats for a variety of bat species. Public policies are needed to ensure effective conservation of biodiversity, biological processes, and the ecosystem services provided by local fauna from the lower lands to the mountain peaks.

Fertility and reproductive rate of Varroa mite, Varroa destructor, in native and exotic honeybee, Apis mellifera L., colonies under Saudi Arabia conditions.

Varroa mite is the most destructive pest to bee colonies worldwide. In Saudi Arabia, preliminary data indicated high infestation levels in the exotic honeybee colonies; such as Apis mellifera carnica and Apis mellifera ligustica, compared to native honeybee subspecies Apis mellifera jemenitica, which may imply higher tolerance to Varroasis. In this study, fertility and reproductive rate of Varroa mite, Varroa destructor, in capped brood cells of the native honeybee subspecies were investigated and compared with an exotic honeybee subspecies, A. m. carnica. Mite fertility was almost alike (87.5% and 89.4%) in the native and craniolan colonies respectively. Similarly, results did not show significant differences in reproduction rate between both subspecies (F = 0.66, Pr > F = 0.42). Number of adult Varroa daughters per fertile mother mite was 2.0 and 2.1 for native and craniolan honeybee subspecies respectively. This may indicate that mechanisms of keeping low infestation rates in the native honeybee colonies are not associated with Varroa reproduction. Therefore, potential factors of keeping lower Varroa infestation rates in native honey bee subspecies should be further investigated.

Interspecific competition between alien Pallas’s squirrels and Eurasian red squirrels reduces density of the native species

When alien species introduced into a new environment have a strong niche overlap with ecologically similar native species, interspecific competition can cause a decrease in abundance and distribution of native species. Pallas’s squirrel (Callosciurus erythraeus) was introduced in Northern Italy where it currently co-occurs with native Eurasian red squirrels (Sciurus vulgaris). The alien species is known for its invasiveness but so far negative effects of Pallas’s squirrels on native tree squirrels have not been demonstrated. Here, we compare demographic parameters of red squirrel populations between sites without (red-only sites) and with (red-Pallas’s sites) C. erythraeus and present results of trapping and removal of Pallas’s squirrel and its effects on red squirrel population dynamics. The native species was patchily distributed and absent in many trapping sites occupied by the Pallas’s squirrel. Red squirrels occurred at much lower densities and showed reduced adult survival in areas of co-occurrence than in red-only sites, but there were no differences in reproductive rate. Removing invasive squirrels throughout the study period resulted in re-colonisation by the native species only in some trapping sites, and several alternatives to explain the lack of a marked increase in population size are discussed. This study is the first to provide evidence that presence of Pallas’s squirrel reduces viability of local red squirrel populations.

Root-Lesion Nematodes Suppress Cabbage Aphid Population Development by Reducing Aphid Daily Reproduction

Empirical studies have shown that belowground feeding herbivores can affect the performance of aboveground herbivores in different ways. Often the critical life-history parameters underlying the observed performance effects remain unexplored. In order to better understand the cause for the observed effects on aboveground herbivores, these ecological mechanisms must be better understood. In this study we combined empirical experiments with a modeling approach to analyze the effect of two root feeding endoparasitic nematodes with different feeding strategies on the population growth of the aboveground feeding specialist aphid Brevicoryne brassicae on Brassica nigra. The aim was to test whether emerging differences in life history characteristics (days until reproduction, daily reproduction) would be sufficient to explain observed differences in aphid population development on plants with and without two species of nematodes. Aphid numbers were lower on plants with Pratylenchus penetrans in comparison to aphid numbers on plants with Meloidogyne spp. A dedicated experiment showed that aphid daily reproduction was lower on plants with P. penetrans (3.08 offspring female–1 day–1) in comparison to both uninfested plants and plants with Meloidogyne spp. (3.50 offspring female–1 day–1). The species-specific reduction of aphid reproduction appeared independent of changes in amino acids, soluble sugars or the glucosinolate sinigrin in the phloem. An individual-based model revealed that relatively small differences in reproduction rate per female were sufficient to yield a similar difference in aphid populations as was found in the empirical experiments.

Same barcode, different biology: differential patterns of infectivity, specificity and pathogenicity in two almost identical parasite strains

Two Norwegian isolates of the monogenean Gyrodactylus salaris Malmberg, 1957 with identical cytochrome c oxidase subunit I barcodes from different hosts, show highly divergent biological and behavioural characteristics. The Lierelva parasite strain, typically infecting Atlantic salmon, Salmo salar L., grew exponentially on Atlantic salmon, but the Pålsbufjorden parasite strain, commonly infecting Arctic charr, Salvelinus alpinus L., grew slowly on both hosts and was non-pathogenic to Atlantic salmon. Both parasite strains reproduced successfully on Arctic charr, but the Atlantic salmon-infecting Lierelva strain grew faster on both hosts. Experiments with isolated worms revealed differences in reproductive rates which may account for the observed population differences. Atlantic salmon parasites consistently gave birth at an earlier age than the Arctic charr parasites, with the differential increasing from 1day for the first birth up to 2–4days for the third birth. Arctic charr-infecting parasites were more active on Atlantic salmon than salmon parasites on Arctic charr, a behavioural strategy leading to enhanced G. salaris mortality. Sequencing of 10kb of nuclear genomic markers revealed only four single nucleotide polymorphisms, confirming that isolates of G. salaris with differences in fitness traits influencing establishment, fecundity and behaviour may be remarkably similar at a molecular level. The framework for reporting and control of G. salaris requires re-appraisal in light of the discovery of variants with such divergent biology.

Nesting success and productivity of Tucuman Parrots (Amazona tucumana) in high-altitude forests of Argentina: do they differ from lowland Amazona parrots?

Most of our knowledge of reproduction of wild parrots in the Neotropics comes from studies of tropical lowland species, with few studies addressing species of high-altitude forests. We studied the reproductive biology of Tucuman Parrots (Amazona tucumana) in north-western Argentina between 2004 and 2009. We obtained data on reproductive output for 86 nests and on causes of mortality for 94 nests. Mean clutch-size per nesting attempt was 3.6 eggs ± 1.0 (s.d.). Hatching success (proportion of eggs laid that hatch) was 0.77 ± 0.17. Fledging success (proportion of nestlings that fledge) was 0.83 ± 0.13. The overall breeding success (mean number of fledglings per laying female per year) was 2.3 ± 0.8. Overall finite nesting success (daily survival rate to the power of the nesting length) was 0.53 ± 0.27, and chick finite nesting success rate was 0.74 ± 0.22. We did not find differences in reproductive rate between Tucuman Parrots and other species of Amazona parrot from lowland habitats. Productivity and nesting success of Tucuman Parrots had high values in some years and low values in others. This was probably related to fruiting events of Podocarpus parlatorei—a critical food item. The main causes of nesting failure were predation (16%) and abandonment (12%). Our results suggest that for several species of Amazona in lowland habitats, predation and poaching may be the main limiting factors whereas climatic factors and food availability may contribute most to nesting failure at higher altitudes.

The effect of different pesticides on reproduction of entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are generally considered beneficial nematodes. These beneficial nematodes can serve in integrated pest management (IPM) in agro-ecosystems. The effect of chemical insecticides (11 different pesticides) on Steinernema sp. (EBN-1e), and Heterorhabditis bacteriophora (EBN-10k) was determined under laboratory conditions. Generally, EBN-1e Steinernema strain was more tolerant to different tested insecticides than Heterorhabditis strain. The survival of IJs was more than 90% after treatement with Captan, Methomyl, Mancozeb, Benomyl, Trimiltox forte and Diafenthiuron, for EBN-1e nematode strain, while Chlorfluazuron decreased its survival to less than 5%. In contrast, the survival of Heterorahbditis strain was less than the Steinernema strain. There were significant differences in reproduction rates between EBN-1e and EBN-10k exposed to different chemical insecticides. The EBN-1e strain had higher reproduction rate than EBN-10k in all treatments. In general, there was significant difference in reproductive rates between the species concentrations (500 IJs and 1000 IJs) exposed to different chemicals or between exposure times (48 h. and 96 h.)

Mink with Divergent Activity Levels have Divergent Reproductive Strategies

AbstractStable individual differences in activity levels within populations have been linked to differences in reproductive rate or parental care in several species, including American mink (Neovison vison). Fur‐farmed mink are good models for studying such effects because they yield large sample sizes and readily allow investigations into maternal behaviour, reproductive success, offspring performance and the relationships between these factors. On farms, very inactive individuals generally have smaller litters, and this held true in our study populations. We tested two competing hypotheses to explain this: (1) inactive individuals are failing to cope with a challenging environment and experiencing chronic stress and/or depression‐like ‘apathy’; this predicts female‐skewed litters, poorer maternal care, higher infant mortality and poorer infant growth and (2) inactive individuals do not have reduced fitness but instead employ an alternative adaptive reproductive strategy, trading off offspring quantity for quality; this predicts enhanced maternal care, reduced infant mortality and enhanced infant growth. Inactive females’ kits, especially their sons, grew faster than active females’, even after statistically controlling for litter size; and by 21 d, inactive and active dams’ litters no longer differed in total biomass, despite the former’s smaller litter sizes. In kit retrieval tests, inactive females were faster than active dams to reach their sons (as well as more likely to contact their sons than their daughters: a bias towards male kits not evident in the active dams). Furthermore, kit growth rates and dam latencies to touch them co‐varied, suggesting the existence of consistent differences in maternal style across inactive and active dams. Hypothesis 2 was thus supported: inactive females favour offspring quality over quantity, investing more resources in fewer kits, particularly males. This potentially boosts their sons’ adult fitness. More broadly for laboratory‐based studies, possible ‘captivity effects’ on the fitness correlates of activity and other personality traits are discussed.

Reproductive Rates in Australian Rodents Are Related to Phylogeny

BackgroundThe native rodents of Australia are commonly divided into two groups based on the time of their colonization of the Sahulian continent, which encompasses Australia, New Guinea, and the adjacent islands. The first group, the “old endemics,” is a diverse assemblage of 34 genera that are descended from a single colonization of the continent during the Pliocene. A second group, the “new endemics,” is composed of several native Rattus species that are descended from a single colonization during the Pleistocene. Finally, a third group is composed of three non-native species of Rattus and Mus introduced into Australia by humans over the last 200 years. Previous studies have claimed that the three groups differ in their reproductive rates and that this variation in rates is associated with the unique environmental conditions across Australia. We examined these hypotheses using phylogenetically controlled methods.Methodology and ResultsWe examined the relationship between the reproductive rates of the Australian rodents and the environmental variations across the continent, as well as the epoch of their colonization of the continent. Our results revealed no significant correlation with environmental variables but a significant association between colonization age and all the reproductive parameters examined.DiscussionBased on a larger phylogeny of the subfamily Murinae, we showed that significant differences in reproductive rates among colonization groups are shared with their closest relatives outside Sahul. Therefore, the lower reproductive rates in the old endemics are more likely to be the result of phylogenetic history and conservation of traits than an adaptation to the Australian environment. In the new endemics, we found a trend of increasing reproductive rates with diversification. We suggest that the differences in reproductive rates of the old endemic rodents and the native Rattus represent alternative adaptive strategies that have allowed them to utilize similar ecological niches across Australia.

Bats of Mesa Verde National Park, Colorado: Composition, Reproduction, and Roosting Habits

We determined the bat fauna at Mesa Verde National Park (Mesa Verde) in 2006 and 2007, characterized bat elevational distribution and reproduction, and investigated roosting habits of selected species. We captured 1996 bats of 15 species in mist nets set over water during 120 nights of sampling and recorded echolocation calls of an additional species. The bat fauna at Mesa Verde included every species of bat known west of the Great Plains in Colorado, except the little brown bat (Myotis lucifugus). Some species showed skewed sex ratios, primarily due to a preponderance of males. Thirteen species of bats reproduced at Mesa Verde. Major differences in spring precipitation between the 2 years of our study were associated with differences in reproductive rates and, in some species, with numbers of juveniles captured. Reduced reproductive effort during spring drought will have a greater impact on bat populations with the forecasted increase in aridity in much of western North America by models of global climate change. We radiotracked 46 bats of 5 species to roosts and describe the first-known maternity colonies of spotted bats (Euderma maculatum) in Colorado. All 5 species that we tracked to diurnal roosts relied almost exclusively on rock crevices rather than trees or snags, despite the presence of mature forests at Mesa Verde and the use of trees for roosts in similar forests elsewhere by some of these species. Comparisons with past bat surveys at Mesa Verde and in surrounding areas suggest no dramatic evidence for effects of recent stand-replacing fires on the composition of the bat community.

Population growth rate and relative virulence of the two South African biotypes of Russian wheat aphid, Diuraphis noxia, and bird cherry-oat aphid, Rhopalosiphum padi, on resistant and non-resistant barley

In South Africa a new biotype of the Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), RWASA2, has appeared which exhibits an improved performance compared to the original biotype (RWASA1 ) on wheat containing the Dn1 resistance gene. We examined population growth rates as well as damage caused by RWASA1 and RWASA2, in addition to a different aphid species, the bird cherry-oat aphid (BCA), Rhopalosiphum padi L. (Hemiptera: Aphididae), on three RWA-resistant barley [Hordeum vulgare L. (Poaceae)] lines (STARS-9577B, STARS-0502B, and STARS-9301B) and one susceptible control (PUMA). RWASA2 had a higher reproductive rate than RWASA1 on all barley lines tested, which is consistent with previous results on wheat. Two of the RWA-resistant lines (STARS-0502B and STARS-9301B) also exhibited a similar resistance phenotype against BCA. In our experiments, severe chlorosis and leaf roll appeared earlier on the control PUMA barley variety as a result of RWASA2 feeding than was the case with RWASA1, probably due to the differences in reproductive rate. Although chlorosis appeared earlier on resistant plants after RWASA2 feeding, this symptom developed much faster during RWASA1 feeding on all three resistant lines tested. As chlorosis did not correlate well with aphid population numbers, we surmise that the differential chlorosis effects may be related to differences in the amount of saliva introduced by the two aphid clones during feeding. Our results indicate that the difference between RWASA2 and RWASA1 are broader than a 'gene for gene' interaction with the Dn1 resistance (R) gene in wheat, and that these biotypes also differ in important aspects of their biology.

Spatial abilities, cognition and the pattern of Neanderthal and modern human dispersals

Neanderthals and anatomically modern humans (AMHs) are very closely related, although their skeletal morphology is distinct enough for them to be classified as separate species. Their physical differences, including the architecture of the skull and post-cranial skeletal proportions, do not explain the extinction of the Neanderthals as a species, however. The post-cranial morphology of the Neanderthals, which is generally believed to reflect an active lifestyle under cold conditions, falls within the range of modern human variation. Their cranial capacities are essentially identical and skull morphology does not convey any obvious adaptive advantage to either species. The existence of other, less easily discernible biological traits that might have contributed to the extinction of the Neanderthals – such as differences in reproductive rates or developmental histories – cannot be ruled out, but are not supported by current data. Behaviourally (culturally) based explanations for the process of replacement of Neanderthal populations by AMHs center on archaeological evidence for more complex patterns of social organisation, associated with the use of symbols and the development of new technologies. This paper explores the link between social complexity, spatial distribution and cognition during the Late Pleistocene, suggesting a mechanism whereby cognitive differences between hominid species may have arisen.

Heterogeneity of lifetime reproductive performance, its components and associations with wool production and liveweight of Merino ewes

The heterogeneity in lifetime (2–6 years of age) reproductive performance within three research flocks maintained at the Agricultural Research Centre, Trangie, in central-western New South Wales, was used to establish the potential to improve flock reproductive performance by identifying performance segments for either selection or for differential management. The data comprised a total of 32 716 records from 7322 ewes, collected over the period from 1977 to 2003. Within each of the flocks, there were large differences (P &lt; 0.001) in lifetime net reproduction rate, and each of its components (fertility, fecundity and lamb survival), between each of the net reproduction rate quartiles. The difference in net reproduction between the ewes in the top quartile and those in the bottom quartile was equivalent to an additional lamb per ewe annually. These differences in reproduction rate between the quartiles were not related to pre-joining liveweight or condition score. Higher reproductive rates were associated with a cost to clean fleece weight, although the estimated effects on fibre diameter were small. Opportunities to use this variation to improve reproduction rates are discussed and include retaining high-performing ewes longer in the breeding flock, removing poor performers and targeting management interventions towards ewes that will yield the largest responses.

Reproductive Rates of Russian Wheat Aphid (Hemiptera: Aphididae) Biotypes 1 and 2 on a Susceptible and a Resistant Wheat at Three Temperature Regimes

The reproductive rates of Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), Biotype 1 (RWA 1) and Biotype 2 (RWA 2) were compared in the laboratory at three temperature regimes on a Russian wheat aphid resistant cultivar ('Prairie Red') and a susceptible cultivar ('TAM 107'). The objective of this study was to expose RWA 1 and RWA 2 to three temperature regimes and two levels of resistance to find whether there were reproductive differences that may occur within each biotype as well as differences in reproduction between biotypes. In addition, temperature effects of the Dn4 gene on biotype reproduction were noted. Differences in reproductive rates between the two biotypes seem to be driven by temperature. For both biotypes, longevity and reproductive rate parameters, except for intrinsic rate of increase, were lower at the 24-29 degree C temperature regime than the 13-18 degree C and 18-24 degree C temperature regimes. The intrinsic rate of increase was higher for both biotypes at the 18-24 degree C and 24-29 degree C temperature regimes than at the 13-18 degree C temperature regime. Reproductive rates between biotypes were similar at the two higher temperature regimes, but the fecundity for RWA 1 was less than RWA 2 at the 13-18 degree C temperature. The change in fecundity rates between RWA 1 and RWA 2 at lower temperatures could have ecological and geographical implications for RWA 2.

Reproductive Rates of Russian Wheat Aphid (Hemiptera: Aphididae) Biotypes 1 and 2 on a Susceptible and a Resistant Wheat at Three Temperature Regimes

The reproductive rates of Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), Biotype 1 (RWA 1) and Biotype 2 (RWA 2) were compared in the laboratory at three temperature regimes on a Russian wheat aphid resistant cultivar (‘Prairie Red’) and a susceptible cultivar (‘TAM 107′). The objective of this study was to expose RWA 1 and RWA 2 to three temperature regimes and two levels of resistance to find whether there were reproductive differences that may occur within each biotype as well as differences in reproduction between biotypes. In addition, temperature effects of the Dn4 gene on biotype reproduction were noted. Differences in reproductive rates between the two biotypes seem to be driven by temperature. For both biotypes, longevity and reproductive rate parameters, except for intrinsic rate of increase, were lower at the 24–29°C temperature regime than the 13–18°C and 18–24°C temperature regimes. The intrinsic rate of increase was higher for both biotypes at the 18–24°C and 24–29°C temperature regimes than at the 13–18°C temperature regime. Reproductive rates between biotypes were similar at the two higher temperature regimes, but the fecundity for RWA 1 was less than RWA 2 at the 13–18°C temperature. The change in fecundity rates between RWA 1 and RWA 2 at lower temperatures could have ecological and geographical implications for RWA 2.

Geographic Variation in Populations of Microcebus murinus in Madagascar: Resource Seasonality or Bergmann's Rule?

Gray mouse lemurs (Microcebus murinus) occur in western Madagascar from the evergreen littoral rain forests at the southern tip of the island to the seasonal dry deciduous forests of the west and northwest. The wide geographic distribution allows researchers to investigate whether ecogeographic variations reflect adaptations to ambient temperatures, as a proxy for constraints of thermoregulation, or to rainfall, as a proxy of food availability. We compared body mass, number of litters/yr, and longevity for 3 populations: 1 from the evergreen littoral rain forest of the south (Mandena: annual mean temperature 23°C, 1600 mm rain/yr), 1 from the dry deciduous forest of the west (Kirindy/CFPF: 25°C, 800 mm), and 1 from the dry deciduous forest of northwestern Madagascar (Ampijoroa: 27°C, 1200 mm). Body mass decreases with increasing ambient temperature from south to north (Mandena > Kirindy/CFPF > Ampijoroa). The number of litters/yr was highest in the littoral rain forest (2 or 3 litters/yr) and decreased with decreasing rainfall (Mandena > Ampijoroa > Kirindy/CFPF). Life expectancy is lowest in the littoral forest (13% recaptures of mouse lemurs between years) and high (ca. 30–40% recaptures between years) in the dry forests (Mandena < Kirindy/CFPF and Ampijoroa). We postulate that constraints of thermoregulation result in the latitudinal gradient of body mass. Reduced resource productivity or seasonality is reflected in differences in reproductive rates, which seemed to be traded off against longevity. Thus body mass, longevity, and reproductive parameters respond differently to ambient conditions.

Monoxenic culture of Pratylenchus sudanensis on carrot disks, with evidence of differences in reproductive rates between geographical isolates

Monoxenic culture of Pratylenchus sudanensis on carrot disks, with evidence of differences in reproductive rates between geographical isolates

Comparative analysis of gonadal and adrenal activity in the black and white rhinoceros in North America by noninvasive endocrine monitoring

AbstractPatterns of fecal reproductive steroid metabolites and adrenal corticoids were characterized for 12‐ to 24‐month periods in black (n = 10 male, 16 female) and white (n = 6 male, 13 female) rhinoceroses at 14 institutions. All black rhinoceros females exhibited at least some ovarian cyclicity on the basis of fecal progestogen analysis (range, 2–12 cycles/yr). However, cycles often were erratic, with many being shorter (&lt;20 days; 18% of cycles) or longer (&gt;32 days; 21%) than the average of 26.8 ± 0.5 days (n = 104 cycles). Five females exhibited periods of acyclicity of 2–10‐month duration that were unrelated to season. One complete and seven partial pregnancies were evaluated in the black rhinoceros. Fecal progestogens increased over luteal phase concentrations after 3 months of gestation. Females resumed cyclicity within 3 months postpartum, before calves were weaned (n = 5). Approximately half of white rhinoceros females (6 of 13) showed no evidence of ovarian cyclicity. Of the cycles observed, 5 were “short” (32.8 ± 1.2 days) and 24 were “long” (70.1 ± 1.6 days). Only two females cycled continuously throughout the study. One had both long (n = 9) and short (n = 2) cycles, whereas the other exhibited long cycles only (n = 5). Fecal estrogen excretion was variable, and profiles were not useful for characterizing follicular activity or diagnosing pregnancy in either species. Males of both species showed no evidence of seasonality on the basis of fecal androgen profiles. Androgen metabolite concentrations were higher (P &lt; 0.05) in the black (27.6 ± 6.9 ng/g) than in the white (16.8 ± 3.1 ng/g) rhinoceros. An adrenocorticotropin hormone challenge in four black rhinoceros males demonstrated that the clearance rate of corticoid metabolites into feces was ∼24 hours. Fecal corticoid concentrations did not differ between males and females, but overall means were higher in the black (41.8 ± 3.1 ng/g) than in the white (31.2 ± 1.7 ng/g) rhinoceros. In summary, fecal steroid analysis identified a number of differences in hormonal secretory dynamics between the black and white rhinoceros that may be related to differences in reproductive rates in captivity. Most black rhinoceros females exhibited some cyclic ovarian activity. In contrast, few white rhinoceroses demonstrated evidence of regular estrous cyclicity, and those females that were active had comparatively long cycles. Results also suggest that fecal corticoid concentrations reflect adrenal activity and may be species specific. Continued studies are needed to determine whether fecal corticoid measurements will be useful for understanding the cause of inconsistent gonadal activity in these two species. Because all but three (15.8%) of the white rhinoceroses evaluated in this study were less than 20 years of age compared to 73.1% (19 of 26) of the black rhinoceroses, the impact of age on reproductive and adrenal activity also needs to be evaluated further. Zoo Biol 20:463–486, 2001. © 2002 Wiley‐Liss, Inc.