Usefulness of marine protected areas as tools for preserving the highly endangered limpet,Patella ferruginea,in the Mediterranean Sea

Patella ferruginea is the most endangered endemic marine invertebrate of western Mediterranean rocky shores. From 2012 to 2015, we performed a census and an ecological study for this gastropod mollusc in the Zembra Archipelago National Park in Tunisia, where a large population still remains. In 1986, a total of 20,000 individuals were estimated, with 0.7?ind/m², 4.4?cm adult mean size and low recruitment rate. In 2009, the estimated population reached 38,559 individuals with 2.65?ind/m², 5.42?cm adult mean size and high recruitment rate. During the present work, 43,790 individuals were estimated in 2012, 27,359 in 2013, 33,170 in 2014 and 40,404 in 2015, with an average density ranging from 0.1 to 8.5 individuals per square metre, but reaching as many as 25?ind/m² on some shores. This makes the archipelago one of the most important Mediterranean ‘hot spots’ for P. ferruginea, as it has a large and well-conserved population of this species. Variability of the population size is influenced by various biotic and abiotic factors, but is principally impacted by poaching of the species. The poachers target individuals larger than 6?cm in length, and the sex ratio study has shown that over 70% of individuals become females at that size. In addition, high recruitment rates were recorded in 2012 and 2013, but these decreased in 2014 and 2015, although population numbers show the opposite pattern. Moreover, growth rate is low and P. ferruginea may need many years to reach a large adult size. The loss of reproductive potential due to poaching inevitably causes a significant imbalance in the limpet population. Our results indicate the importance of the National Park for P. ferruginea and underline the need for this species to be protected and monitored over a long period to provide the most appropriate management measures.     

Overcompensatory recruitment and generation delay in discrete age-structured population models

 The effect of overcompensatory recruitment and the combined effect of overcompensatory recruitment and generation delay in discrete nonlinear age-structured population models is studied. Considering overcompensatory recruitment alone, we present formal proofs of the supercritical nature of bifurcations (both flip and Hopf) as well as an extensive analysis of dynamics in unstable parameter regions. One important finding here is that in case of small and moderate year to year survival probabilities there are large regions in parameter space where the qualitative behaviour found in a general n+1 dimensional model is retained already in a one-dimensional model. Another result is that the dynamics at or near the boundary of parameter space may be very complicated. Generally, generation delay is found to act as a destabilizing effect but its effect on dynamics is by no means unique. The most profound effect occurs in the n-generation delay cases. In these cases there is no stable equilibrium X ^* at all, but whenever X ^* small, a stable cycle of period n+1 where the periodic points in the cycle are on a very special form. In other cases generation delay does not alter the dynamics in any substantial way. Received 25 April 1995; received in revised form 21 November 1995     

Demography of the long‐lived conifer Agathis ovata in maquis and rainforest,New Caledonia

Abstract. The endemic New Caledonian conifer Agathis ovata occurs as an emergent tree in fire‐prone shrublands (maquis), and fire‐sensitive rainforest. Growth, survivorship and recruitment over 5 yr were compared for populations from forest and maquis on ultramafic substrates in New Caledonia to investigate whether demographic behaviour varied in response to the strongly contrasting forest and shrubland environments. Growth of seedlings and of small (30–100 cm height) and large (100 cm height; 5 cm DBH) saplings was slow, but varied significantly among stages, site types and years. The greatest difference in growth rates was among stages, seedlings growing 0.34 cm.yr^?1, small saplings 1.06 cm.yr^?1 and large saplings 2.13 cm.yr^?1. Tree DBH increased by only 0.05 cm.yr^?1 and, based on these rates, individuals with DBH of 30 cm are estimated to be more than 700 yr old. Few trees (3.5%) produced cones in any year and seedling recruitment was low, but some recruitment was recorded each year in both maquis and forest. Rates of recruitment per parent were highest in forest (1.28.yr^?1, cf 0.78.yr^?1), but the higher density of trees in maquis meant that overall recruitment was greater there (92 ha^?1.yr^?1, cf 56 ha^?1.yr^?1). Seedling mortality ranged from 0.9 to 2.9% among years with no significant difference between maquis and forest. No sapling mortality was recorded, but annual tree mortality ranged from 0 to 1.4%. Evidence from a recently burned site indicated that while trees may survive fire, seedlings and saplings do not. Post‐fire seedling recruitment per ha from surviving trees was four times lower than in unburned sites, but growth rates were four times higher. Similar demographic attributes, including high survivorship, low growth rate and low rates of recruitment over a long reproductive life, characterize Agathis ovata populations in both maquis and rainforest in New Caledonia and are indicative of a broad tolerance of light environments that is unusual among tree species. These demographic attributes help to explain the long‐term persistence of the species in these strongly contrasting habitats.     

Spawning aggregations of squid (Sepioteuthis australis) populations: a continuum of ‘microcohorts’

The aim of this study was to determine how size, age, somatic and reproductive condition, abundance and egg production of southern calamary spawning aggregations changed during the spawning season in each of 2 years. During the spawning period in at least one of the years there was a decline as much as 20% in average size, 50% in somatic condition, 28–34% in size-at-age, 26–29% in reproductive status, as well as abundance and reproductive output of the stock declining during the spawning season. However, this change was not a function of the population becoming reproductively exhausted, as the aggregation was composed of different individuals with different biological characteristics. In each month the average age of individuals was ca. 6 mo, indicating that squid that had hatched at different times had entered the spawning aggregations, suggesting that the aggregation was made-up of a succession of microcohorts. Currently, management of many squid populations assumes that there is a single cohort in the aggregation. Therefore, estimating stock biomass at the start of the spawning season cannot be used as the population is constantly changing as micro-cohorts move into the aggregation. An instantaneous estimate of the spawning biomass, independent of fishing activity may be obtained by quantifying the density of deposited eggs. The strategy of individuals with a diversity of life history characteristics coming together in a single spawning aggregation may ensure the phenotypic and genetic diversity required to guarantee successful recruitment of this short-lived species. Therefore, temporally structured protection from harvest throughout the spawning season will ensure maintenance of this population diversity.     

Patterns of emergence,import of egg energy and energy export via emerging dragonfly populations in a tropical pond

The most abundant dragonflies Brachythemis contaminata, Orthetrum sabina, Diplacodes trivialis, Pantala flavescens and Trithemis festiva in the tropical pond Idumban emerged from November to April during the years 1973,1974 and 1975. The date of initiation of emergence of all the species was synchronized and tied to the events following the north west monsoon in November. During the seasons '73–74 and '74–75, as many as 10,693 and 7,910 adults emerged; females outnumbered the males in all the 5 species; male populations of B. contaminata, O. sabina, D. trivialis, P. flavescens and T. festiva represented 47, 48, 46, 49 and 44% during the '73–74 season, 48, 48, 46, 46 and 49% during the '74–75 season, respectively. The adult dragonflies equivalent to 2,442 Kcal emerged from the Pond during the season '73–74. Of this, B. contaminata contributed 30%, D. trivialis 7%, O. sabina 12%, P. flavescens 23% and T. festiva 28%. For the season '74–75, the dragonflies equivalent to 1,602 Kcal emerged from the Pond and the contribution was in the following order: B. contaminata: 31%, O. sabina: 8%, D. trivialis: 13%, P. flavescens: 27% and T. festiva: 21%. Import of energy due to inoculation of B. contaminata eggs into the Pond Idumban was 73 Kcal/ year and the output from the Pond via emerging B. contaminata population alone amounted to 620 Kcal/ year; the net energy loss from the Pond was 548 Kcal/ year. During either season, as much as 99.7% of B. contaminata eggs failed to attain adulthood due to infertility (5.8%), unhatchability (12%) and predation during the egg and nymphal stages (82.5%). During the study, the GPP of the Pond was 26,073 Kcal/m²/ year, and output of energy through emergence of 5 dragonfly species amounted to 0.0045 Kcal/m²/year, i.e. 0.00002% of the GPP is lost through the emerging carnivorous odonates; comparable values available for the emerging detritivorous chironomids, herbivorous dipterans and mayflies fall between 1.0 and 0.1%.     

Yearly variation in recruitment and its effect on population dynamics inYoldia notabilis (Mollusca: Bivalvia), analyzed using projection matrix model

Long-term variation in recruitment was estimated by constructing projection matrices for a marine bivalve, Yoldia notabilis, at two stations in Otsuchi Bay, northeastern Japan, and the effects of its variation on population dynamics were examined using a simple matrix model. The matrix model was developed from the Leslie matrix, in which the population growth rate λ was expressed as a function of recruitment rate r₀. The equilibrium recruitment rate r_s, or the recruitment rate required to maintain population at constant size (λ=1), was expressed by the reciprocal of the reproductive value of a newly recruited individual. The estimates of r_s for the field population were lower at the shallower station than at the deeper station, reflecting higher survivorship and fecundity. Past recruitment rate estimated both by the field samplings for 3 years and by the back-calculation from the current age structure for over 10 years showed large yearly variation, ranging between 0 and 58.6×10⁻⁴. The estimates were larger than r_s, and hence, large enough to increase population size (λ>1) only in approximately one-third of the estimated years. This suggests that the population has been maintained by occasional successful recruitment occurring once every few years.     

Ecological energetics of a daphnia ambigua population

Based on population data, growth and development rate, and feeding and respiratory rates, energy budgets were constructed for a wild population of Daphnia ambigua Scourfield in a pond at The University of Kansas, Lawrence. The relationships between monthly efficiency of energy transfer and food or temperature were analyzed by multiple and partial correlation. Annual energy consumption, based on seston concentration, by D. ambigua population amounted to 410.1 kcal/m³. Of this, 8.4% was used in somatic growth (Pg) and egg production (Pr); 2.7% was lost as exuvia (Pex) and 17.1% was lost in respiration (R). The amount of energy consumed lost as ammonia excretion and faeces was 1.4 and 70.4%, respectively. The total annual energy flow (assimilation) was 115.6 kcal/ m³; annual assimilation efficiency (28.2%) was lower than values reported for other planktonic Crustacea. Annual net production efficiency was 39.3% (32.8%, excluding exuvia). The annual P/R ratio was 0.64 to 0.66. The mean daily P accounted for 9.3% of the mean daily gross primary production of phytoplankton. The mean daily assimilation accounted for 23.6% of gross primary production, or 56.2% of net primary production.     

Interacting effect of wolves and climate on recruitment in a northern mountain caribou population

There is limited research on the influence of Pacific‐based climate in large herbivore populations. Additionally, much of our understanding on the effect of large‐scale climate on ungulate population dynamics has occurred on forage‐limited rather than predator‐limited populations. We compared the influence of the Pacific Decadal Oscillation (PDO), North Pacific Index, and local weather on recruitment in a predator‐limited mountain‐dwelling caribou Rangifer tarandus caribou population in the Yukon Territory, Canada, across a range of wolf Canis lupus densities. A large‐scale wolf removal program allowed us to examine the role of Pacific climate and weather when wolves were reduced to ～15% of their pre‐removal levels. Recruitment was best explained by the interaction of wolf density and April‐PDO, with wolf density explaining the most deviance. Predicted recruitment during good springs was 0.45 (SE = 0.04) during wolf removal and 0.29 (SE = 0.03) with no wolf removal. During poor springs (low PDO, increased snow depth) predicted recruitment was 0.55 (SE = 0.10) during wolf removal and 0.12 (SE = 0.03) with no wolf removal. With non‐altered wolf densities, there was a positive relationship between April‐PDO and recruitment due to reduced snow depth at calving, allowing parturient females to disperse up in elevation away from predators. When wolf densities were substantially reduced there was a slight negative relationship between April‐PDO and recruitment, possibly due to a more rapid vegetation green‐up reducing the temporal availability of highly nutritious forage necessary for lactation and subsequent calf growth. Attempts to find general relationships between climate and ungulate population dynamics have proven difficult due to different ecological mechanisms by which climate affects individuals across populations. Temporally varying factors, such as predator density, may also play an important role in uncovering the mechanistic relationship between climate and population dynamics.     

Population fragmentation may reduce fertility to zero in Banksia goodii — a demonstration of the Allee effect

All individuals of all known populations of Banksia goodii were assessed for seed production. Small populations produced no or only a few seeds per unit canopy area. Effects of population size on seed production per unit area and seed production per plant were present over the whole range of population sizes, indicating that even in large populations seed production may still not be at its maximum. Resource differences could not explain this disproportionate decrease in seed production with decline in population size, because there were no differences in soil properties and understorey or overstorey cover between the small and large populations. Although plants in small and large populations were similar in size, seed production per plant was much lower in small populations. This was not because plants in small populations produced fewer cones but because the fraction of these cones that was fertile was much lower. Five of the nine smallest populations (<200 m²) produced no fertile cones over the last 10 years. The number of seeds per fertile cone did not depend on population size. The results are discussed in relation to pollination biology.     

SEED BANK,SURVIVORSHIP, AND SIZE DISTRIBUTION OF A NEBRASKA POPULATION OF IMPATIENS CAPENSIS (BALSAMINACEAE)

The growth and survivorship of a population of Impatiens capensis were followed in eastern Nebraska. Soil cores were taken within the population to estimate the size of the seed bank. The number of seeds in the soil remained relatively constant from April through October, with a mean of 200 seeds/m². The seed bank size corresponded to observed seedling densities in the following years. Twenty permanent plots were established within the population and censused for three years, 1983–1985. Seedling recruitment to the population was similar in 1983 and 1984 but 30% higher in 1985. The seedling densities of plots were uncorrelated from year to year. Survivorship in 1983 followed a Deevey Type I pattern. Almost one-third of the population survived until chasmogamous reproduction. Plant size (stem height) was measured monthly on all individuals during 1983. The frequency distribution of stem height was positively skewed as long as growth was exponential. When the growth rate slowed, the distribution became more normal.     

Influence of maternal mass and condition on energy transfer in Weddell seals

1. Environmental variation influences food abundance and availability, which is reflected in the reproductive success of top predators. We examined maternal expenditure, offspring mass and condition for Weddell seals in 2 years when individuals exhibited marked differences in these traits. 2. For females weighing > or = 355 kg there was a positive relationship between maternal post-partum mass (MPPM) and lactation length, but below this there was no relationship, suggesting that heavier females were able to increase lactation length but lighter females were restricted to a minimum lactation period of 33 days. 3. Overall, females were heavier in 2002, but in 2003 shorter females were lighter than similar-sized females in 2002 suggesting that the effects of environmental variability on foraging success and condition are more pronounced in smaller individuals. 4. There was no relationship between MPPM and pup birth mass, indicating pre-partum investment did not differ between years. However, there was a positive relationship between MPPM and pup mass gain. Mass and energy transfer efficiency were 10.2 and 5.4% higher in 2002 than 2003, which suggests costs associated with a putatively poor-resource year were delayed until lactation. 5. Heavier females lost a higher proportion of mass during lactation in both years, so smaller females may not have been able to provide more to their offspring to wean a pup of similar size to larger females. 6. MPPM had only a small influence on total body lipid; therefore, regardless of mass, females had the same relative body composition. Females with male pups lost a higher percentage of lipid than those with female pups, but by the end of lactation female pups had 4.5% higher lipid content than males. 7. It appears that for Weddell seals the consequences of environmentally induced variation in food availability are manifested in differences in maternal mass and expenditure during lactation. These differences translate to changes in pup mass and condition at weaning with potential consequences for future survival and recruitment.     

Extended breeding and recruitment periods of fishes on a low latitude coral reef

The temporal dynamics of fish recruitment to equatorial Indo-Pacific coral reefs are not well known. This paper documents fish recruitment over a 2.5-year period in Kimbe Bay (PNG) and shows that it is much less seasonal than is typically described for higher latitude coral reefs. Two families, wrasses (Labridae) and damselfishes (Pomacentridae), which accounted for 90% of all non-cryptic reef fish settlers, exhibited contrasting patterns. Most wrasse species had year-round recruitment with irregular peaks in abundance between November and May. Damselfish species showed a wider range of recruitment patterns, but most had negligible recruitment during the wet season (December–February), followed by one or two recruitment peaks between May and November. Species with longer seasonal recruitment periods exhibited higher cumulative levels of recruitment. For three focal damselfish species, reproductive output was reduced during the wet season, but this alone did not account for the low recruitment at this time. The lack of damselfish recruitment during the wet season is hypothesised to be due to a combination of reduced reproductive output and increased larval mortality associated with monsoonal conditions. The results indicate that there are consistent family-wide recruitment strategies that may play a significant role in the dynamics of populations in equatorial waters.     

Age estimations of wild pallid sturgeon (Scaphirhynchus albus,Forbes & Richardson 1905) based on pectoral fin spines,otoliths and bomb radiocarbon: inferences on recruitment in the dam‐fragmented Missouri River

An extant stock of wild pallid sturgeon Scaphirhynchus albus persists in the fragmented upper Missouri River basin of Montana and North Dakota. Although successful spawning and hatch of embryos has been verified, long‐term catch records suggest that recruitment has not occurred for several decades as the extant stock lacks juvenile size classes and is comprised exclusively of large, presumably old individuals. Ages of 11 deceased (death years 1997–2007) wild S. albus (136–166 cm fork length) were estimated based on pectoral fin spines, sagittal otoliths and bomb radiocarbon (¹⁴C) assays of otoliths to test the hypothesis that members of this stock are old and to provide inferences on recruitment years that produced the extant stock. Age estimations based on counts of presumed annuli were about 2 years greater for otoliths (mean = 51 years, range = 43–57 years) than spines (mean = 49 years, range = 37–59 years). Based on ¹⁴C assays, confirmed birth years for all individuals occurred prior to 1957, thus establishing known longevity of at least 50 years. Estimated age based on presumed otolith annuli for one S. albus was validated to at least age 49. Although ¹⁴C assays confirmed pre‐1957 birth years for all S. albus, only 56% of estimated ages from spines and 91% of estimated ages from otoliths depicted pre‐1957 birth years. Both ageing structures were subject to under‐ageing error (up to 15 years). Lack of or severe curtailment of S. albus recruitment in the upper Missouri River basin since the mid‐1950s closely parallels the 1953–1957 timeframe when a mainstem reservoir was constructed and started to fill. This reservoir may function as a system‐wide stressor to diminish recruitment success of S. albus in the upper Missouri River basin.     

Investigating the Effect of Recruitment Variability on Length-Based Recruitment Indices for Antarctic Krill Using an Individual-Based Population Dynamics Model

Antarctic krill (Euphausia superba; herein krill) is monitored as part of an on-going fisheries observer program that collects length-frequency data. A krill feedback management programme is currently being developed, and as part of this development, the utility of data-derived indices describing population level processes is being assessed. To date, however, little work has been carried out on the selection of optimum recruitment indices and it has not been possible to assess the performance of length-based recruitment indices across a range of recruitment variability. Neither has there been an assessment of uncertainty in the relationship between an index and the actual level of recruitment. Thus, until now, it has not been possible to take into account recruitment index uncertainty in krill stock management or when investigating relationships between recruitment and environmental drivers. Using length-frequency samples from a simulated population – where recruitment is known – the performance of six potential length-based recruitment indices is assessed, by exploring the index-to-recruitment relationship under increasing levels of recruitment variability (from ±10% to ±100% around a mean annual recruitment). The annual minimum of the proportion of individuals smaller than 40 mm (F40 min, %) was selected because it had the most robust index-to-recruitment relationship across differing levels of recruitment variability. The relationship was curvilinear and best described by a power law. Model uncertainty was described using the 95% prediction intervals, which were used to calculate coverage probabilities and assess model performance. Despite being the optimum recruitment index, the performance of F40 min degraded under high (>50%) recruitment variability. Due to the persistence of cohorts in the population over several years, the inclusion of F40 min values from preceding years in the relationship used to estimate recruitment in a given year improved its accuracy (mean bias reduction of 8.3% when including three F40 min values under a recruitment variability of 60%).     

Life history and population biology of the giant ostracod Leuroleberis zealandica (Baird, 1850) (Myodocopida)

A population of this large myodocopid ostracod was studied over 2 yr by random core-sampling of the medium sand bottom at Kaikoura, New Zealand. Leuroleberis zealandica (Baird) passes through seven instars, it is sexually mature only in the final instar and sexes were distinguishable from instar IV. Males and females were equally abundant except in the final instar when the morphologically distinct males were rarely found. The population consists of three cohorts at any one time and each cohort appears to split into fast- and slow-growing individuals during the sixth instar resulting in life times of 1.8–2.0 and 2.7–3.1 yr, respectively. Females produce only one brood of 37 eggs on average per life time that are carried throughout the 5–6 month development period during which there is no loss of embryos. Recruitment is discrete with most broods released in midsummer when the population density may exceed 350·0.1 m^?2. A second lesser recruitment may occur in early spring in some years. Hatched juveniles released from the female grow rapidly to instar IV within 6 months and, although size increments at each moult are proportionally similar, intermoult periods tend to increase with size with some variation according to seasonal growth rates. Instar life tables constructed from instar density data showed a large difference in the frequency of embryos initiating each cohort, very different mortalities at recruitment between cohorts, and that the mortality rates between instars I and VI of different cohorts appear to be independent of density. The biology of Leuroleberis is compared with the few published accounts of myodocopid biology. In addition, several aspects of the biology of myodocopids are reviewed. These include numbers of instars in different taxa, within-instar sexual size disparities, numbers of broods per female life time, egg and brood sizes in relation to adult female size in various taxa, and the question of post-adult moulting.     

Population dynamics of two Scottish Ultramafic (serpentine) rarities with contrasting life histories

Summary

The paper reports demographic studies of the endemic Cerastium nigrescens and the very rare Arenaria norvegica ssp. norvegica on the Keen of Hamar ultramafic outcrop on Unst, Shetland from June 1994 to November 1996. Plants of Cerastium nigrescens showed a Deevey type II curve and mature plants had a half-life of 3.8 years. Plants of Arenaria norvegica ssp. norvegica showed a Deevey type I curve with high mortality after flowering in the second year. There was some evidence of increased mortality during droughts but this had little impact on the total population. Seed production and seedling recruitment for both species was good throughout the study period. Seed bank measurements ranged from 12–13 m² for Cerastium nigrescens and 24–43 m^-2 for Arenaria norvegica ssp. norvegica. The study showed that there was no immediate threat to the populations of the two species but because of their isolated occurrence they are susceptible to extinction and should be carefully monitored.     

Demography and social organization of free-ranging Lemur catta in the Beza Mahafaly Reserve,Madagascar

In 1987, a long-term study of the demography of Lemur catta was begun in southern Madagascar. Eighty-five ringtailed lemurs were captured, marked, and released. Adult age classes were estimated using patterns of dental attrition. Including young, 155 individuals from nine groups were identified and monitored over 18 months. The study population of the reserve remained stable, with a growth rate of 0.98. Group sizes ranged from nine to 22 individuals (mean 14). Home ranges were larger (32 ha) and population densities lower (135/km²) than those for previously studied populations, and there was a relationship between habitat quality (e.g., no. of large trees) and these factors. At the beginning of the study, there were more adult males than females, but the sex ratio reached 1.00 by the last census. Females first gave birth at 3 years of age, and 80% or more of the females gave birth in 2 consecutive years. Fifty-two percent of the infants died in the first year and, given preliminary findings, only 40% of those born reach adulthood. Age-specific fertility patterns were similar to those reported for anthropoid primates. Forty-seven percent of the adult males migrated or were missing within a year. This included 78% of the 3–4 year olds and 38% of older age classes. No females were observed to migrate. One group split during the study. Demographic patterns are discussed and related to patterns in other populations of ringtailed lemurs as well as in anthropoids.     

High haplotype diversity with fine-scale structure in a recently established population of an endangered orchid

New populations of endangered plants may establish outside of protected areas if a suitable habitat becomes available. However, it is unclear whether such populations are genetically uniform, as a result of a founder effect, or whether they contain genetic variation resulting from continuous gene flow from source populations, and subsequent recruitment after establishment. We addressed this by examining haplotype variation in the endangered orchid, Anacamptis robusta, which has formed a new population outside of its protected area within the past 20 years. To assess population growth, the number of A. robusta flowering plants were counted every year for 22 years in both the new population and populations within the reserve. Haplotype diversity and fine-scale structure were examined with spatial autocorrelation analysis, both in the new population and representative populations from the protected area. The number of flowering individuals in the new population increased from 9 to 2,277 between 2003 and 2012, whereas within the reserve flowering population sizes varied between years. Seventeen of 23 haplotypes detected for A. robusta were detected in the new population, with seven of these occurring more frequently in the new population than reserve populations. In the new population, there was strong fine-scale spatial structure of haplotypes, similar to patterns found in large populations from the protected area, suggesting multiple colonization events and subsequent local recruitment. This highlights that ongoing demographic and genetic monitoring of plant populations is vital to improve our understanding of population colonization and the conservation of narrow endemics.     

Effects of density-dependence and climate on the dynamics of a Svalbard reindeer population

To determine the main factors affecting the population dynamics of Svalbard reindeer, we analysed 21 yr of annual censuses, including data on population size, recruitment rate (calves per female) and mortality (number of deaths), from the Reindalen reindeer population. In accordance with previous studies on population dynamics of Svalbard reindeer, we found large inter-annual variation in population size, mortality and recruitment rates within the study area. Population size decreased in years with low recruitment rate as well as high winter mortality and vice versa. Apparently. the fluctuations were due to both direct density-dependent food limitation and variation in winter climate associated with high precipitation and icing of the feeding range. We found no delayed density-dependence or effect of climatic conditions during summer on the population dynamics. The mortality during die-off years was mainly of calves and very old individuals, indicating that the population was more vulnerable to high die oft in years following high recruitment rate. These results suggest an unstable interaction between the reindeer population and its food supply in these predator-free environments.     

Demographics,reproduction, growth,and abundance of Jollyville Plateau salamanders (Eurycea tonkawae)

Insights into the ecology and natural history of the neotenic salamander, Eurycea tonkawae, are provided from eight years of capture‐recapture data from 10,041 captures of 7,315 individuals at 16 sites. Eurycea tonkawae exhibits seasonal reproduction, with peak gravidity occurring in the fall and winter. Size frequency data indicated recruitment occurred in the spring and summer. Open‐population capture‐recapture models revealed a similar seasonal pattern at two of three sites, while recruitment was dependent on flow at the third site. Females can reach sexual maturity within one year, and oviposition likely takes place below ground. The asymptotic body length of 1,290 individuals was estimated as 31.73 mm (at ca. two years of age), although there was substantial heterogeneity among growth trajectories. Longevity was approximately eight years, and the median age for a recaptured adult was 2.3 years. Abundance estimated from closed‐population and robust‐design capture‐recapture models varied widely within and among sites (range 41–834), although, surprisingly, dramatic changes in abundance were not observed following prolonged dry periods. Seasonal migration patterns of second‐year and older adults may help explain lower ratios of large individuals and higher temporary emigration during the latter half of the year, but further study is required. Low numbers of captures and recaptures precluded the use of open‐population models to estimate demographic parameters at several sites; therefore, closed‐population (or robust‐design) methods are generally recommended. Based on observations of their life history and population demographics, E. tonkawae seems well adapted to conditions where spring flow is variable and surface habitat periodically goes dry.