High Adult Survival Research Articles

Recruitment patterns in the Mediterranean deep-water alga Cystoseira zosteroides

Although recruitment is considered an essential process regulating populations of many marine species, there is still a lack of knowledge about the ultimate factors that influence it. This is especially true for seaweeds, where population dynamics studies are also lacking. The main objective of this study was to investigate the main mechanisms driving the recruitment patterns of an emblematic deep-water alga in the NW Mediterranean, Cystoseira zosteroides, and its influence on their population dynamics. Five C. zosteroides populations were monitored annually at different sites along the coast of Spain by using permanent transects over 3–4 years. Some of these populations suffered mass mortality events from natural or anthropogenic disturbances, allowing us to study the influence of such events. Our findings agreed with the expected results for a long-lived species. Under low frequency of disturbances, C. zosteroides populations displayed few fluctuations over time given the longevity of the adults, and they were poorly influenced by the dynamics of early life stages because of negative density-dependent control of conspecifics. Moreover, disturbances had a great influence on population dynamics because the removal of adults decreased the effects of density-dependent processes and enhanced the recruitment. Nonetheless, a high mortality was found for early life stages (~50 % year−1), contrasting with the high survival of adults (~90 % year−1). This study confirmed the slow population dynamics of these deep assemblages, demonstrated the influence of density in the C. zosteroides population dynamics and highlighted their vulnerability to the increase in natural and human-induced disturbances.

Spatial distribution and settlement strategies in willow ptarmigan

In heterogeneous landscapes individuals select among several habitat patches. The fitness rewards of these choices are assumed to play an important role in the distribution of individuals across landscapes. Individuals can either use environmental cues to directly assess the quality of breeding sites, or rely on social cues to guide the settlement decision. We estimated the density of adult birds and per capita reproductive success of willow ptarmigan over 5–15 years in 42 survey areas, nested within 5 spatially separated populations in south-central Norway. Our aims were to (1) examine spatial and temporal patterns of variation in densities of adult birds (i.e., the breeding densities) and reproductive success (juveniles/pair) measured in autumn and (2) evaluate which habitat distribution model best described the distribution of willow ptarmigan across heterogeneous mountain landscapes. Variation in density of adult birds was primarily attributable to variation between survey areas which could arise from spatial heterogeneity in adult survival or as a consequence of spacing behavior of juveniles during the settlement stage. In contrast, reproductive success was more variable between years and did not vary consistently between survey areas once year effects were accounted for. The lack of any relationship between the density of adult birds and reproductive success supported the predictions of an ideal free distribution (IFD), implying that within years, the mean reproductive success was approximately equal across survey areas. However, analysis based on Taylor's power law (i.e., the relationship between logarithms of spatial variance and mean density of adult birds) suggested that aggregation was stronger than expected under IFD. This implies that the relative change in density of adult birds was larger in areas with high mean densities than in areas with low densities. The exact mechanisms causing this statistical pattern are unclear, but based on the breeding biology of willow ptarmigan we suggest that yearlings are attracted to areas of high densities during the settlement period in spring. Our study was conducted during a period of low overall density and we suggest that this pattern might be particular to such situations. This implies that the presence of conspecifics might represent a cue signaling high adult survival and thus high habitat quality.

Adélie penguin (Pygoscelis adeliae) survival rates and their relationship to environmental indices in the South Shetland Islands, Antarctica

Seabird life history is typified by low fecundity, high adult survival rates, and relatively long lives. Such traits act as buffers, enabling persistence of populations under variable environmental conditions. Numerous studies, however, have suggested strong sensitivity of seabirds to environmental variability. In the Antarctic Peninsula region, for example, Adélie penguin (Pygoscelis adeliae) populations have declined during the last three decades, attributed largely to rapid changes in environmental conditions and food availability. We use 30 years of mark-recapture data from known-age individuals in the South Shetland Islands and capture-mark-recapture models to estimate survival rates with respect to such environmental variation. We investigated specifically whether negative trends in survival rates were evident and whether indices of global, regional, and local environmental conditions considered important for Adélie penguin survival explained the variability in survival rates. Overall, negative trends in juvenile survival were evident, but adult survival rates exhibited high interannual variability. Indices of sea ice extent had the strongest correlations with survival rates, particularly Weddell Sea ice extent during spring among adults (r = 0.62) and during winter for juveniles (r = 0.46). An analysis of deviance, however, suggested that single environmental covariates explained <30 % of the observed variation in the full mark-recapture models. Despite positive effects of sea ice extent on survival rates of Adélie penguins, limited explanatory power of several environmental conditions previously identified as important for Adélie penguin survival underscores the difficulty of predicting future population responses in this region of rapid environmental change.

Survival, demography, and growth of gopher tortoises (Gopherus polyphemus) from three study sites with different management histories

The Journal of Wildlife Management 78(7):1151–1160; 2014; DOI: 10.1002/jwmg.773 Research Article Survival, Demography, and Growth of Gopher Tortoises (Gopherus polyphemus) from Three Study Sites with Different Management Histories TRACEY D. TUBERVILLE, 1 University of Georgia’s Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, USA BRIAN D. TODD, Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, One Shields Ave, Davis, CA 95616, USA SHARON M. HERMANN, Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA WILLIAM K. MICHENER, University Libraries, 1312 Basehart SE, Albuquerque, NM 87106, USA CRAIG GUYER, Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA ABSTRACT Recovery or sustainable management of wildlife populations often entails management of habitat on which they depend. In this regard, turtles pose unique conservation challenges because of their life histories. The combination of late maturity, low survival when young, and dependence on high adult survival suggests they may be slow to respond demographically to conventional habitat management. Thus, long- term studies are necessary to understand population dynamics and recovery potential in these species. We used 5–11 years of mark-recapture data from 3 populations to evaluate survivorship, demography, and somatic growth of gopher tortoises (Gopherus polyphemus). Green Grove and Wade Tract (southwest GA) are ecological reserves with a history of land management compatible with tortoises. In contrast, Conecuh National Forest (south-central AL) is a closed-canopy pine plantation with prior intensive site preparation but where management intervention improved habitat for tortoises during the study. Apparent survival was high for mature tortoises (87–98%) compared to immature tortoises (70–82%). Adults comprised 57–79% of individuals captured, with Green Grove and Wade Tract populations dominated by larger individuals but Conecuh having a more uniform size distribution. The largest adults captured at Conecuh (297 mm maximum carapace length [CL]) were smaller than the largest adults from Green Grove (337 mm CL) or Wade Tract (341 mm CL), although characteristic growth constants from von Bertalanffy models were similar among sites. We suggest these results indicate a recovering population at Conecuh, where habitat conditions for gopher tortoises have improved despite a legacy of intense predation by humans and reduced habitat quality at the inception of this national forest. Further, we recommend using a combination of short- term and long-term monitoring metrics to assess population recovery in such long-lived species. O 2014 The Wildlife Society. KEY WORDS demography, gopher tortoise, Gopherus polyphemus, growth, habitat management, population recovery, survivorship. Turtles are among the most imperiled vertebrate group globally, with nearly 66% classified as “vulnerable to extinction” or worse (International Union for the Conserva- tion of Nature [IUCN] 2012). Turtles offer a unique set of conservation challenges due to their slow life history strategies. The combination of high hatchling and early juvenile mortality, high adult survivorship and longevity, delayed sexual maturity, and low reproductive output (Gibbons 1987, Iverson 1991) makes them vulnerable to demographic perturbations (Brooks et al. 1991, Congdon Received: 29 May 2013; Accepted: 26 June 2014 Published: 26 August 2014 E-mail: tubervil@uga.edu Tuberville et al. Survival, Demography, and Growth in Tortoises et al. 1993, but see Fordham et al. 2007). Likewise, these traits also limit the ability of turtle populations to recover even after threats have abated (Bailey and Guyer 1998, Hall et al. 1999, Tucker et al. 2001, Troe¨ng and Rankin 2005). The gopher tortoise (Gopherus polyphemus) is restricted to the Coastal Plain physiographic province in the southeastern United States and was historically associated with the longleaf pine (Pinus palustris) ecosystem. Less than 3% of the original longleaf pine ecosystem remains, mostly as small, isolated fragments (Ware et al. 1993, Means 2006). Because of this habitat loss, many of the more than 200 associated vertebrate species, including the gopher tortoise, have also experienced dramatic declines (Means 2006). In 1987, the western population of the gopher tortoise was federally listed as threatened, and in 2011, the United States Fish and

Climate warming decreases the survival of the little auk (Alle alle), a high Arctic avian predator.

Delayed maturity, low fecundity, and high adult survival are traits typical for species with a long-life expectancy. For such species, even a small change in adult survival can strongly affect the population dynamics and viability. We examined the effects of both regional and local climatic variability on adult survival of the little auk, a long-lived and numerous Arctic seabird species. We conducted a mark-resighting study for a period of 8 years (2006-2013) simultaneously at three little auk breeding sites that are influenced by the West Spitsbergen Current, which is the main carrier of warm, Atlantic water into the Arctic. We found that the survival of adult little auks was negatively correlated with both the North Atlantic Oscillation (NAO) index and local summer sea surface temperature (SST), with a time lag of 2 and 1 year, respectively. The effects of NAO and SST were likely mediated through a change in food quality and/or availability: (1) reproduction, growth, and development of Arctic Calanus copepods, the main prey of little auks, are negatively influenced by a reduction in sea ice, reduced ice algal production, and an earlier but shorter lasting spring bloom, all of which result from an increased NAO; (2) a high sea surface temperature shortens the reproductive period of Arctic Calanus, decreasing the number of eggs produced. A synchronous variation in survival rates at the different colonies indicates that climatic forcing was similar throughout the study area. Our findings suggest that a predicted warmer climate in the Arctic will negatively affect the population dynamics of the little auk, a high Arctic avian predator.

Reducing bias in survival under nonrandom temporary emigration.

Despite intensive monitoring, temporary emigration from the sampling area can induce bias severe enough for managers to discard survival parameter estimates toward the terminus of the times series (terminal bias). Under random temporary emigration, unbiased parameters can be estimated with CJS models. However, unmodeled Markovian temporary emigration causes bias in parameter estimates, and an unobservable state is required to model this type of emigration. The robust design is most flexible when modeling temporary emigration, and partial solutions to mitigate bias have been identified; nonetheless, there are conditions were terminal bias prevails. Long-lived species with high adult survival and highly variable nonrandom temporary emigration present terminal bias in survival estimates, despite being modeled with the robust design and suggested constraints. Because this bias is due to uncertainty about the fate of individuals that are undetected toward the end of the time series, solutions should involve using additional information on survival status or location of these individuals at that time. Using simulation, we evaluated the performance of models that jointly analyze robust design data and an additional source of ancillary data (predictive covariate on temporary emigration, telemetry, dead recovery, or auxiliary resightings) in reducing terminal bias in survival estimates. The auxiliary resighting and predictive covariate models reduced terminal bias the most. Additional telemetry data were effective at reducing terminal bias only when individuals were tracked for a minimum of two years. High adult survival of long-lived species made the joint model with recovery data ineffective at reducing terminal bias because of small-sample bias. The naive constraint model (last and penultimate temporary emigration parameters made equal), was the least efficient, although still able to reduce terminal bias when compared to an unconstrained model. Joint analysis of several sources of data improved parameter estimates and reduced terminal bias. Efforts to incorporate or acquire such data should be considered by researchers and wildlife managers, especially in the years leading up to status assessments of species of interest. Simulation modeling is a very cost-effective method to explore the potential impacts of using different sources of data to produce high-quality demographic data to inform management.

Efficacy of aerosol applications of methoprene and synergized pyrethrin against Tribolium castaneum adults and eggs.

Experiments were performed to determine the efficacy of a single aerosol application of the insecticides methoprene and piperonyl butoxide-synergized pyrethrin, alone or in combination, and the insecticide carrier, Isopar M, against Tribolium castaneum (Herbst), the red flour beetle. The initial test exposed adults to insecticide treatments and placed male/female pairs in flour. All adults exposed to synergized pyrethrin were knocked down for at least 24 h after exposure but they recovered. High adult survival and similar average numbers of living F1 progeny were produced regardless of treatment exposure. In a separate test, insecticide treatments were directly applied to newly laid eggs, which resulted in the suppression of egg hatch. Synergized pyrethrin was the most effective insecticide (P < or = 0.001) for suppressing egg hatch. The effect of flour on insecticide activity to eggs and consequent insect development was also evaluated. An amount of 0.01 g of flour in the exposure arena, 62-cm2 area, was not sufficient for individuals to develop beyond the early larval stages, regardless of the treatment. As the flour amount in the arena increased from 1 to 5 g, the number of eggs that could develop to the adult stage increased, but this number was significantly lower in the insecticide treatments than in the control or carrier treatments. The results of the later tests indicate a high efficacy of the insecticides alone or in combination on T. castaneum egg hatch and development to the adult stage.

South temperate birds have higher apparent adult survival than tropical birds in Africa

Life history theory predicts an inverse relationship between annual adult survival and fecundity. Globally, clutch size shows a latitudinal gradient among birds, with south temperate species laying smaller clutches than north temperate species, but larger clutches than tropical species. Tropical birds often have higher adult survival than north temperate birds associated with their smaller clutches. However, the prediction that tropical birds should also have higher adult survival than south temperate birds because of smaller clutch sizes remains largely untested. We measured clutch size and apparent annual breeding adult survival for 17 south temperate African species to test two main predictions. First, we found strong support for a predicted inverse relationship between adult survival and clutch size among the south temperate species, consistent with life‐history theory. Second, we compared our clutch size and survival estimates with published estimates for congeneric tropical African species to test the prediction of larger clutch size and lower adult survival among south temperate than related tropical species. We found that south‐temperate species laid larger clutches, as predicted, but had higher, rather than lower, apparent adult survival than related tropical species. The latter result may be an artefact of different approaches to measuring survival, but the results suggest that adult survival is generally high in the south temperate region and raises questions about the importance of the cost of reproduction to adult survival.

Mass gained during breeding positively correlates with adult survival because both reflect life history adaptation to seasonal food availability

Both mass (as a measure of body reserves) during breeding and adult survival should reflect variation in food availability. Those species that are adapted to less seasonally variable foraging niches and so where competition dominates during breeding, will tend to have a higher mass increase via an interrupted foraging response, because their foraging demands increase and so become more unpredictable. They will then produce few offspring per breeding attempt, but trade this off with higher adult survival. In contrast, those species that occupy a more seasonal niche will not gain mass because foraging remains predictable, as resources become superabundant during breeding. They can also produce more offspring per breeding attempt, but with a trade-off with reduced adult survival. We tested whether the then predicted positive correlation between levels of mass gained during seasonal breeding and adult survival was present across 40 species of tropical bird measured over a 10-year period in a West African savannah. We showed that species with a greater seasonal mass increase had higher adult survival, controlling for annual mass variation (i.e. annual variation in absolute food availability) and variation in the timing of peak mass (i.e. annual predictability of food availability), clutch size, body size, migratory status and phylogeny. Our results support the hypothesis that the degree of seasonal mass variation in birds is probably an indication of life history adaptation: across tropical bird species it may therefore be possible to use mass gain during breeding as an index of adult survival.

The demography of Yellow Wagtails Motacilla flava on abandoned fields in northern European Russia

Capsule Apparent survival rates of Yellow Wagtails breeding in abandoned fields in Russia are determined by previous breeding success.Aims To examine apparent survival and its link to previous breeding success in Yellow Wagtails breeding in abandoned fields in the Vologda region, northern European Russia.Methods We ringed and measured apparent survival of Yellow Wagtails at two abandoned agricultural sites over eight years (2005–2012). We modelled the impact of age, nest stage, and time of season on daily nest survival rates.Results Predation was the main cause of nest failure. Nest daily survival rate was highest at the beginning of the breeding season. Overall nest survival probability was 0.40 ± 0.02. Adult apparent survival after successful breeding was 0.42 ± 0.06 and after unsuccessful breeding this was 0.13 ± 0.06.Conclusion Reproductive success can be regarded as the crucial demographic parameter of the local Yellow Wagtail population in northern European Russia. Apparent survival after successful breeding is significantly higher than after unsuccessful breeding, because unsuccessful breeders probably move to new breeding sites the following year. High adult survival may be particularly important to Yellow Wagtail population dynamics in the study region, because second breeding attempts are apparently unusual.

Delayed juvenile dispersal and monogamy, but no cooperative breeding in white-breasted mesites (Mesitornis variegata)

Although cooperative breeding is known from only about 9 % of bird species, it has received substantial attention because individuals foregoing their own reproduction to help others represent a long-standing evolutionary puzzle. We studied group formation, breeding system, spatial distribution and several life-history traits of white-breasted mesites (Mesitornis variegata). Based on field observations across 3 years, we found that white-breasted mesites live in year-round stable pairs, and that groups are formed by juvenile philopatry. As other family-living birds, M. variegata exhibit a slow pace-of-life, characterized by high annual adult survival, low productivity, long chick dependence and extended parental care. However, although reproduction is monogamous and juveniles showed interest in their parents’ nests, we found no evidence of cooperative breeding. We suggest that slow life-histories, extended parental care and year-round territoriality predispose juvenile mesites to delay dispersal. However, adult intolerance toward older juveniles may prevent them from adopting a cooperative lifestyle. Comparisons with other species of mesite indicate that monogamy and delayed juvenile dispersal are necessary, but not sufficient for the evolution of cooperative breeding in this family of birds, and that particular ecological and social conditions have facilitated the transition from pair-living to a type of group that may represent a stepping stone in the evolution of cooperative breeding in mesites and other birds.

Understanding the effects of a new grazing policy: the impact of seasonal grazing on shrub demography in the Inner Mongolian steppe

Summary Grazing by livestock is a common land use in arid and semi‐arid areas. Developing sustainable grazing regimes that conserve vegetation and maintain productivity is therefore important in these ecosystems. To solve environmental problems induced by overgrazing in Chinese semi‐arid regions, the Chinese government has recently implemented a new policy of seasonal grazing, with no grazing from April to July. While this policy has been implemented in huge areas, its consequences for grazed plant populations have not been assessed so far. We evaluated the demographic consequences of seasonal grazing for Caragana intermedia, a long‐lived dominant shrub serving as a main food source for livestock in Inner Mongolia, China. Controlled seasonally grazed and ungrazed populations were monitored during 2007–2009, and their vital rates were compared. We then constructed integral projection models (IPMs) to analyse the effects of seasonal grazing on population dynamics. Seasonal grazing negatively affected two vital rates: seedling survival and seedling recruitment were 25–71% and 69–91% lower in the seasonally grazed treatment than in the ungrazed situation, respectively. Seasonal grazing had a minimal effect on adult survival and growth, but improved juvenile survival by 8–31%. Despite its effects on several vital rates, seasonal grazing did not significantly affect long‐term population growth rates (λ), which remained close to unity in both grazed and ungrazed areas based on deterministic and stochastic analyses. An elasticity analysis showed that population growth rate was mainly governed by the high survival of large adults. Results of Life Table Response Experiments (LTREs) revealed that variation in population growth rates across treatments and years was more strongly governed by temporal differences than by grazing. Synthesis and applications. Our study showed that the relatively large changes in vital rates induced by seasonal grazing did not affect population growth rates. Caragana intermedia populations can be sustained under the seasonal grazing regime probably because the grazing intensity is moderate and because this species has a high probability of adult survival under grazing. Plant species with similar life‐history traits to C. intermedia are likely to offer good opportunities for sustainable seasonal grazing regimes in arid and semi‐arid inland ecosystems.

How to improve agri-environment schemes to achieve meadow bird conservation in Europe? A case study in the Saône valley, France

Ongoing meadow bird demographic trends in Europe raise the question of the effectiveness of public policy aiming to halt biodiversity loss. In this study, we attempted to understand the success and failures in one of the first French Agri-Environment Schemes (AES), 20 years after its implementation. After annually postponing grass harvesting to 1 or 15 July in 25 % of a 3,000-ha lowland meadow system, we observed a clear demographic increase in the Eurasian Curlew Numenius arquata, the Whinchat Saxicola rubetra and the Yellow Wagtail Motacilla flava. No positive effects were recorded for the Skylark Alauda arvensis, the Corn Bunting Miliaria calandra and the Reed Bunting Emberiza schoeniclus, possibly as a result of increased competition with Whinchats and Yellow Wagtails, and the Corncrake Crex crex declined sharply despite the implemented measures. The successful results were attributed, for the Curlew to the species’ early nesting and high adult survival, for the Whinchat to the probable support of immigration, and for the Yellow Wagtail to a possible capacity to avoid unfavourable nesting situations. Late breeding and low adult survival may contribute to explain the continuing Corncrake decline. In the study site, late mown AES areas were too small and fragmented to match efficiently the territory aggregations. We recommend to extend AES principles to all the European range of targeted species, even outside the EU, and to develop species-specific spatial strategies.

Negative impacts of hunting and suction-dredging on otherwise high and stable survival rates in Curlew Numenius arquata

Capsule A stable annual survival rate of 90% was estimated for adult Curlew Numenius arquata from 1974 to 2011. Survival was reduced by mechanized cockle harvesting and hunting prior to the UK ban in 1982, but was similar for males and females. Aims To estimate annual and average survival rates for Curlew wintering in North Wales. To test the impacts of protection from hunting (effective 1982), and mechanized cockle dredging on apparent survival and longevity. Methods Thirty-six years' ringing data comprising 2636 bird records were analysed using Cormack Jolly–Seber survival models in mark. Models included variable and trending survival, plus constant-survival models (all years, pre- and post-hunting, sampling effort). The effects of protection from hunting, sampling success, cockle dredging and sex (from biometrics) were investigated, and the results compared with survival in other species and the predictions of demographic population models. Results Averaged annual survival was 89.9% with no significant difference between males and females. Estimated survival increased slightly from 86.9% (se = 0.04) to 90.5% (se = 0.01) and longevity by at least 40% after hunting was banned in 1982. Mechanized cockle harvesting in 1996 reduced apparent survival from 95% (best data estimate: se 0.07) to 81% (se 0.19) for two years, and was correlated with a published analysis showing reduced survival in Oystercatchers. Conclusion Declines observed in overwintering Curlew populations in the UK are not primarily driven by changes in adult survival, and continue despite the increase in survival to > 90% after hunting ceased in 1982. High adult survival rates cannot compensate for poor breeding productivity, and we anticipate poor turnover will lead to future impacts from senescence even in such a long-lived species.

Life history constraints contribute to the vulnerability of a declining North American rattlesnake

Delayed maturation and age-biased dispersal work in concert under past selection to maximize individual fitness and contribute to population viability; however, these life history attributes can become dysfunctional in a dynamic, anthropogenic landscape when important population demographics cannot redistribute in response to novel landscape change. We used long-term monitoring data to estimate age at maturity, potential longevity, survival, and fidelity for the declining eastern diamondback rattlesnake (EDB), Crotalus adamanteus. We used radio telemetry data and known-fate models to examine adult survival, and we combined mark-recapture and radio telemetry data to examine survival and fidelity using a combined recapture/recovery model. Monthly adult survival was higher during the active season (April–November; 99.5%) as compared to the inactive season (December–March; 96.3%), despite a higher probability of detecting human-caused mortalities during the active season. Rattlesnakes matured in 7.1years and potential longevity exceeded 20years. Fidelity estimates indicated mature EDBs had a low probability of dispersing from the study area, while younger, sexually immature individuals were more likely to emigrate. The combination of a slow life history and an ontogenetic shift in emigration suggests EDB life history limits the species’ ability to respond to landscape change, shedding further light on EDB imperilment. Management efforts will benefit from activities that maintain high adult survival. Furthermore, EDB fidelity should be considered in conservation plans, particularly in light of the species’ longevity, as these characteristics suggest that mature EDBs may not readily redistribute at the landscape scale in response to habitat degradation.

Evaluating the Effects of Population Management on a Herbivore Grazing Conflict

Abundant herbivores can damage plants and so cause conflict with conservation, agricultural, and fisheries interests. Management of herbivore populations is a potential tool to alleviate such conflicts but may raise concerns about the economic and ethical costs of implementation, especially if the herbivores are ‘charismatic’ and popular with the public. Thus it is critical to evaluate the probability of achieving the desired ecological outcomes before proceeding to a field trial. Here we assessed the potential for population control to resolve a conflict of non-breeding swans grazing in river catchments. We used a mathematical model to evaluate the consequences of three population management strategies; (a) reductions in reproductive success, (b) removal of individuals, and (c) reduced reproductive success and removal of individuals combined. This model gave accurate projections of historical changes in population size for the two rivers for which data were available. Our model projected that the River Frome swan population would increase by 54%, from 257 to 397 individuals, over 17 years in the absence of population control. Removal of ≥60% of non-breeding individuals each year was projected to reduce the catchment population below the level for which grazing conflicts have been previously reported. Reducing reproductive success, even to 0 eggs per nest, failed to achieve the population reduction required. High adult and juvenile survival probabilities (>0.7) and immigration from outside of the catchment limited the effects of management on population size. Given the high, sustained effort required, population control does not represent an effective management option for preventing the grazing conflicts in river catchments. Our study highlights the need to evaluate the effects of different management techniques, both alone and in combination, prior to field trials. Population models, such as the one presented here, can provide a cost-effective and ethical means of such evaluations.

Life-history strategies of North American elk: trade-offs associated with reproduction and survival

The principle of energy allocation states that individuals should attempt to maximize fitness by allocating resources optimally among growth, maintenance, and reproduction. Such allocation may result in trade-offs between survival and reproduction, or between current and future reproduction. We used a marked population of North American elk (Cervus elaphus) to determine how energetic costs of reproduction in the current year affect survival and reproduction in the subsequent year. Using a multistate mark–recapture model we examined the influence of individual and environmental variation on trade-offs between these 2 life-history traits. We observed no difference in survival probabilities between pregnant and nonpregnant individuals or as a function of recruiting an offspring. Nonetheless, there was a negative effect of recruiting an offspring in the current year on becoming pregnant the following year. Increased body condition, and higher precipitation, contributed to greater probabilities of becoming pregnant in a particular year regardless of reproductive state and previous recruitment. Costs associated with reproduction led to a reduced probability of future reproduction rather than a reduction in survival. These findings are consistent with risk-sensitive reproductive allocation, where adult survival is maintained through variation in reproductive effort resulting in high and stable adult survival and more-variable reproduction.

Managing the long‐term persistence of a rare cockatoo under climate change

Summary1. Linked demographic‐bioclimatic models are emerging tools for forecasting climate change impacts on well‐studied species, but these methods have been used in few management applications, and species interactions have not been incorporated. We combined population and bioclimatic envelope models to estimate future risks to the viability of a cockatoo population posed by climate change, increased fire frequency, beak‐and‐feather disease and reduced management.2. The South Australian glossy black‐cockatoo Calyptorhynchus lathami halmaturinus is restricted to Kangaroo Island, Australia, where it numbers 350 birds and is managed intensively. The cockatoo may be at particular risk from climate change because of its insular geographic constraints and specialised diet on a single plant species, Allocasuarina verticillata. The cockatoo population model was parameterised with mark‐resight‐derived estimates of survival and fecundity from 13 years of demographic data. Species interactions were incorporated by using a climate‐change‐driven bioclimatic model of Allocasuarina verticillata as a dynamic driver of habitat suitability. A novel application of Latin Hypercube sampling was used to assess the model’s sensitivity to input parameters.3. Results suggest that unmitigated climate change is likely to be a substantial threat for the cockatoo: all high‐CO2‐concentration scenarios had expected minimum abundances of &lt;160 birds. Extinction was virtually certain if management of nest‐predating brush‐tail possums Trichosurus vulpecula was stopped, or adult survival reduced by as little as 5%. In contrast, the population is predicted to increase under low‐emissions scenarios.4. Disease outbreak, increased fire frequency and reductions in revegetation and management of competitive little corellas Cacatua sanguinea, were all predicted to exacerbate decline, but these effects were buffered by the cockatoo population’s high fecundity.5. Spatial correlates of extinction risk, such as range area and total habitat suitability, were nonlinearly related to projected population size in the high‐CO2‐concentration scenario.6. Synthesis and applications. Mechanistic demographic‐bioclimatic simulations that incorporate species interactions can provide more detailed viability analyses than traditional bioclimatic models and be used to rank the cost‐effectiveness of management interventions. Our results highlight the importance of managing possum predation and maintaining high adult cockatoo survival. In contrast, corella and revegetation management could be experimentally reduced to save resources.

Bet‐hedging germination in annual plants: a sound empirical test of the theoretical foundations

Seed dormancy is thought to be a key mechanism allowing annual plants to spread extinction risk in unpredictably varying environments. Theory predicts increasing germination fractions with increasing probability of reproductive success but solid empirical evidence is scarce and often confounded with environmental factors. Here we provide an empirical test of bet‐hedging via delayed germination for three annual plant species along a ‘predictability gradient’ in Israel. We excluded confounding environmental and maternal effects by raising inbred seed families and germinating them under controlled conditions. Additionally, we germinated field‐collected seeds in three consecutive seasons to compare their germination with inbred families where maternal effects were removed. Risk of reproductive failure was quantified using demographic data from the field and from second‐generation inbred lines raised in a rainfall gradient in the greenhouse. Our findings were consistent with bet‐hedging theory in that germination fraction was negatively related to species‐ and site‐specific risk of reproductive failure. Both field and hand‐raised seeds of one species exhibited higher dormancy with increasing risk of reproductive failure across sites, and hand‐raised seeds of another species showed the same pattern. The third species exhibited a rather random pattern of germination between years and sites, corresponding to the lack of site‐specific risk of reproductive failure. Species‐specific patterns of dormancy and risk could be related to alternative risk‐spreading strategies such as high adult survival, but were also affected by phylogeny. We provide strong empirical evidence for seed dormancy being a mechanism to reduce the risk of reproductive failure in highly variable environments, but a larger number of rigorous experimental tests of bet hedging germination are needed. Specifically, the genetic basis of bet‐hedging must be shown in species with different life histories, for demonstrating that dormancy is adaptive and how it is modified by other risk‐spreading traits.

Effect of maternal and grandmaternal care on population dynamics and human life-history evolution: A matrix projection model

We present a matrix population model for a single-sex human population comprising non-orphan daughters (whose mothers are alive) and orphan daughters (whose mothers are dead). Orphans suffer higher mortality than non-orphans, which simulates the need for daughters to receive maternal care in order to survive. The way that maternal care affects population dynamics and life-history evolution is then analysed for demographic regimes that encompass large ranges of daughter survival, mother survival and fertility. We provide stable age-distributions of orphans and non-orphans for each regime and perform sensitivity analyses on daughter survival, adult survival and fertility. The results show that natural selection will favour (i) faster daughter independence from maternal care, (ii) higher adult survival at all ages, and (iii) early reproduction to the detriment of late reproduction. We then build scenarios concerning the coevolution of daughter survival and maternal care with adult survival and fertility. We also incorporate grandmaternal care into the model. We show that (i) the acute altriciality of human babies, (ii) the increased maternal care resulting from emergence of complex sociality and (iii) the role played by grandmothers in caring for granddaughters may have led to the emergence of specific human life-history traits: a short reproductive period characterised by a reproductive senescence and menopause, as well as an extended lifespan characterised by a post-reproductive life.