scholarly journals Detecting Resource Limitation in a Large Herbivore Population Is Enhanced With Measures of Nutritional Condition

2021 ◽  
Vol 8 ◽  
Author(s):  
Brendan A. Oates ◽  
Kevin L. Monteith ◽  
Jacob R. Goheen ◽  
Jerod A. Merkle ◽  
Gary L. Fralick ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Resource Limitation ◽  
Remotely Sensed ◽  
Nutritional Condition ◽  
Adult Survival ◽  
Vital Rates ◽  
Bottom Up ◽  
Environmental Covariates ◽  
Demographic Rates

Resource limitation at the population level is a function of forage quality and its abundance relative to its per capita availability, which in turn, determines nutritional condition of individuals. Effects of resource limitation on population dynamics in ungulates often occur through predictable and sequential changes in vital rates, which can enable assessments of how resource limitation influences population growth. We tested theoretical predictions of bottom-up (i.e., resource limitation) forcing on moose (Alces alces) through the lens of vital rates by quantifying the relative influence of intrinsic measures of nutritional condition and extrinsic measures of remotely sensed environmental data on demographic rates. We measured rates of pregnancy, parturition, juvenile, and adult survival for 82 adult females in a population where predators largely were absent. Life stage simulation analyses (LSAs) indicated that interannual fluctuations in adult survival contributed to most of the variability in λ. We then extended the LSA to estimate vital rates as a function of bottom-up covariates to evaluate their influence on λ. We detected weak signatures of effects from environmental covariates that were remotely sensed and spatially explicit to each seasonal range. Instead, nutritional condition strongly influenced rates of pregnancy, parturition, and overwinter survival of adults, clearly implicating resource limitation on λ. Our findings depart from the classic life-history paradigm of population dynamics in ungulates in that adult survival was highly variable and generated most of the variability in population growth rates. At the surface, lack of variation explained by environmental covariates may suggest weak evidence of resource limitation in the population, when nutritional condition actually underpinned most demographics. We suggest that variability in vital rates and effects of resource limitation may depend on context more than previously appreciated, and density dependence can obfuscate the relationships between remotely sensed data and demographic rates.

scholarly journals Breeding transients in capture–recapture modeling and their consequences for local population dynamics

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Daniel Oro ◽  
Daniel F. Doak
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Growth ◽  
Population Growth Rate ◽  
Local Population ◽  
Environmental Stochasticity ◽  
Adult Survival ◽  
Local Survival ◽  
First Reproduction ◽  
Capture Recapture

Abstract Standard procedures for capture–mark–recapture modelling (CMR) for the study of animal demography include running goodness-of-fit tests on a general starting model. A frequent reason for poor model fit is heterogeneity in local survival among individuals captured for the first time and those already captured or seen on previous occasions. This deviation is technically termed a transience effect. In specific cases, simple, uni-state CMR modeling showing transients may allow researchers to assess the role of these transients on population dynamics. Transient individuals nearly always have a lower local survival probability, which may appear for a number of reasons. In most cases, transients arise due to permanent dispersal, higher mortality, or a combination of both. In the case of higher mortality, transients may be symptomatic of a cost of first reproduction. A few studies working at large spatial scales actually show that transients more often correspond to survival costs of first reproduction rather than to permanent dispersal, bolstering the interpretation of transience as a measure of costs of reproduction, since initial detections are often associated with first breeding attempts. Regardless of their cause, the loss of transients from a local population should lower population growth rate. We review almost 1000 papers using CMR modeling and find that almost 40% of studies fitting the searching criteria (N = 115) detected transients. Nevertheless, few researchers have considered the ecological or evolutionary meaning of the transient phenomenon. Only three studies from the reviewed papers considered transients to be a cost of first reproduction. We also analyze a long-term individual monitoring dataset (1988–2012) on a long-lived bird to quantify transients, and we use a life table response experiment (LTRE) to measure the consequences of transients at a population level. As expected, population growth rate decreased when the environment became harsher while the proportion of transients increased. LTRE analysis showed that population growth can be substantially affected by changes in traits that are variable under environmental stochasticity and deterministic perturbations, such as recruitment, fecundity of experienced individuals, and transient probabilities. This occurred even though sensitivities and elasticities of these parameters were much lower than those for adult survival. The proportion of transients also increased with the strength of density-dependence. These results have implications for ecological and evolutionary studies and may stimulate other researchers to explore the ecological processes behind the occurrence of transients in capture–recapture studies. In population models, the inclusion of a specific state for transients may help to make more reliable predictions for endangered and harvested species.

Characterization of elasticity patterns of North American freshwater fishes

2006 ◽  
Vol 63 (9) ◽  
pp. 2050-2066 ◽  
Author(s):  
Luis A Vélez-Espino ◽  
Michael G Fox ◽  
Robert L McLaughlin
Keyword(s):  
Population Growth ◽  
North American ◽  
Growth Rates ◽  
Freshwater Fishes ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Vital Rates ◽  
Population Growth Rates ◽  
North American Freshwater ◽  
Trade Offs

We applied elasticity analysis to 88 North American freshwater fishes to assess the relative impacts of changes in the vital rates on asymptotic population growth. Variance in vital rates was summarized for four distinct functional groups: (i) species with population growth rates strongly sensitive to perturbations in adult survival; (ii) species with population growth rates sensitive to perturbations in overall survival; (iii) species with population growth rates most sensitive to perturbations in juvenile survival; and (iv) species with population growth rates sensitive to perturbations in juvenile survival and fecundity. The results of the present study also showed that (a) elasticity patterns cannot be inferred in a straightforward manner from trade-offs between life-history traits, (b) the sensitivity of a population's growth rate to changes in adult survival and fecundity can be predicted empirically from life span and age at maturity, respectively, (c) elasticities are highly conserved among genera within the same taxonomic family, and (d) there are key divergences between elasticity patterns of freshwater fish and other vertebrate taxa.

scholarly journals Spatial variation in giraffe demography: a test of 2 paradigms

2016 ◽  
Vol 97 (4) ◽  
pp. 1015-1025 ◽  
Author(s):  
Derek E. Lee ◽  
Monica L. Bond ◽  
Bernard M. Kissui ◽  
Yustina A. Kiwango ◽  
Douglas T. Bolger
Keyword(s):  
Population Growth ◽  
Spatial Variation ◽  
Adult Female ◽  
Vital Rate ◽  
Adult Survival ◽  
Continental Scale ◽  
Demographic Rates ◽  
Adult Females ◽  
Calf Survival ◽  
Female Survival

Abstract Examination of spatial variation in demography among or within populations of the same species is a topic of growing interest in ecology. We examined whether spatial variation in demography of a tropical megaherbivore followed the “temporal paradigm” or the “adult survival paradigm” of ungulate population dynamics formulated from temperate-zone studies. We quantified spatial variation in demographic rates for giraffes (Giraffa camelopardalis) at regional and continental scales. Regionally, we used photographic capture-mark-recapture data from 860 adult females and 449 calves to estimate adult female survival, calf survival, and reproduction at 5 sites in the Tarangire ecosystem of Tanzania. We examined potential mechanisms for spatial variation in regional demographic rates. At the continental scale, we synthesized demographic estimates from published studies across the range of the species. We created matrix population models for all sites at both scales and used prospective and retrospective analyses to determine which vital rate was most important to variation in population growth rate. Spatial variability of demographic parameters at the continental scale was in agreement with the temporal paradigm of low variability in adult survival and more highly variable reproduction and calf survival. In contrast, at the regional scale, adult female survival had higher spatial variation, in agreement with the adult survival paradigm. At both scales, variation in adult female survival made the greatest contribution to variation in local population growth rates. Our work documented contrasting patterns of spatial variation in demographic rates of giraffes at 2 spatial scales, but at both scales, we found the same vital rate was most important. We also found anthropogenic impacts on adult females are the most likely mechanism of regional population trajectories.

scholarly journals The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears

2015 ◽  
Vol 282 (1798) ◽  
pp. 20141840 ◽  
Author(s):  
Jacinthe Gosselin ◽  
Andreas Zedrosser ◽  
Jon E. Swenson ◽  
Fanie Pelletier
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Indirect Effects ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Relative Importance ◽  
Direct And Indirect Effects ◽  
Negative Effects ◽  
Hunting Pressure ◽  
Demographic Rates

There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear ( Ursus arctos ). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure ( λ = 0.975; 95% CI = 0.914–1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI.

scholarly journals Population dynamics of the endangered mountain ecotype of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada

2020 ◽  
Author(s):  
Heiko Wittmer ◽  
BN McLellan ◽  
DR Seip ◽  
JA Young ◽  
TA Kinley ◽  
...  
Keyword(s):  
British Columbia ◽  
Population Dynamics ◽  
Rangifer Tarandus ◽  
Population Decline ◽  
Survival Rates ◽  
Adult Survival ◽  
Rangifer Tarandus Caribou ◽  
Vital Rates ◽  
Woodland Caribou ◽  
Annual Survival

We used census results and radiotelemetry locations of >380 collared individuals sampled over the entire distribution of the endangered mountain ecotype of woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) in British Columbia, Canada, to delineate population structure and document the size and trend of the identified populations. We also describe the spatial pattern of decline and the causes and timing of adult mortality and provide estimates of vital rates necessary to develop a population viability analysis. Our results indicate that the abundance of mountain caribou in British Columbia is declining. We found adult female annual survival rates below annual survival rates commonly reported for large ungulates. The major proximate cause of population decline appears to be predation on adult caribou. Spatial patterns of population dynamics revealed a continuous range contraction and an increasing fragmentation of mountain caribou into smaller, isolated subpopulations. The population fragmentation process predominantly occurs at the outer boundaries of the current distribution. Our results indicate that recovery strategies for mountain caribou should be directed at factors contributing to the fragmentation and isolation of mountain caribou populations as well as management strategies aimed at increasing adult survival. © 2005 NRC Canada.

Effects of territorial status and life history on Sandhill Crane (Antigone canadensis) population dynamics in south-central Wisconsin, USA

2019 ◽  
Vol 97 (2) ◽  
pp. 112-120 ◽  
Author(s):  
Michael E. Wheeler ◽  
Jeb A. Barzen ◽  
Shawn M. Crimmins ◽  
Timothy R. Van Deelen
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Demographic Data ◽  
Bird Species ◽  
Adult Survival ◽  
Vital Rates ◽  
Management Actions ◽  
South Central ◽  
Sandhill Cranes

Population growth rate in long-lived bird species is often most sensitive to changes in adult survival. Sandhill Cranes (Antigone canadensis (Linnaeus, 1758)) have long life spans, small broods, and delayed first reproduction. Only territorial adult Sandhill Cranes participate in breeding, and territory acquisition reflects the interplay between the availability of suitable territories and the variation in mortality of adult birds occupying those territories. We estimated vital rates of a population at equilibrium using long-term resightings data (2000–2014; n = 451 marked individuals) in a multistate mark–resight model and used a stage-structured projection matrix to assess how strongly territorial adult survival affects population growth rate. Elasticity analysis indicated territorial birds surviving and retaining territories had a 2.58 times greater impact on population growth compared with the next most important transition rate (survival of nonterritorial adults remaining nonterritorial). Knowing how changes in vital rates of various stage classes will differentially impact population growth rate allows for targeted management actions including encouraging growth in recovering populations, assessing opportunity for recreational harvest, or maintaining populations at a desired level. This study also highlights the value of collecting demographic data for all population segments, from which one can derive reproductive output or growth rate.

scholarly journals Assessing the Viability of the Sarasota Bay Community of Bottlenose Dolphins

2021 ◽  
Vol 8 ◽  
Author(s):  
Robert C. Lacy ◽  
Randall S. Wells ◽  
Michael D. Scott ◽  
Jason B. Allen ◽  
Aaron A. Barleycorn ◽  
...  
Keyword(s):  
Life History ◽  
Population Growth ◽  
Adult Survival ◽  
Model Parameters ◽  
Catastrophic Events ◽  
Demographic Rates ◽  
Sarasota Bay ◽  
Population Demographic ◽  
Over Time

Population models, such as those used for Population Viability Analysis (PVA), are valuable for projecting trends, assessing threats, guiding environmental resource management, and planning species conservation measures. However, rarely are the needed data on all aspects of the life history available for cetacean species, because they are long-lived and difficult to study in their aquatic habitats. We present a detailed assessment of population dynamics for the long-term resident Sarasota Bay common bottlenose dolphin (Tursiops truncatus) community. Model parameters were estimated from 27 years of nearly complete monitoring, allowing calculation of age-specific and sex-specific mortality and reproductive rates, uncertainty in parameter values, fluctuation in demographic rates over time, and intrinsic uncertainty in the population trajectory resulting from stochastic processes. Using the Vortex PVA model, we projected mean population growth and quantified causes of variation and uncertainty in growth. The ability of the model to simulate the dynamics of the population was confirmed by comparing model projections to observed census trends from 1993 to 2020. When the simulation treated all losses as deaths and included observed immigration, the model projects a long-term mean annual population growth of 2.1%. Variance in annual growth across years of the simulation (SD = 3.1%) was due more to environmental variation and intrinsic demographic stochasticity than to uncertainty in estimates of mean demographic rates. Population growth was most sensitive to uncertainty and annual variation in reproduction of peak breeding age females and in calf and juvenile mortality, while adult survival varied little over time. We examined potential threats to the population, including increased anthropogenic mortality and impacts of red tides, and tested resilience to catastrophic events. Due to its life history characteristics, the population was projected to be demographically stable at smaller sizes than commonly assumed for Minimum Viable Population of mammals, but it is expected to recover only slowly from any catastrophic events, such as disease outbreaks and spills of oil or other toxins. The analyses indicate that well-studied populations of small cetaceans might typically experience slower growth rates (about 2%) than has been assumed in calculations of Potential Biological Removal used by management agencies to determine limits to incidental take of marine mammals. The loss of an additional one dolphin per year was found to cause significant harm to this population of about 150 to 175 animals. Beyond the significance for the specific population, demographic analyses of the Sarasota Bay dolphins provide a template for examining viability of other populations of small cetaceans.

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

2016 ◽  
Vol 43 (4) ◽  
pp. 358 ◽  
Author(s):  
Magdalena A. Zabek ◽  
David M. Berman ◽  
Simon P. Blomberg ◽  
Christina W. Collins ◽  
John Wright
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Body Condition Score ◽  
Equus Caballus ◽  
Population Increase ◽  
Adult Survival ◽  
Feral Horses ◽  
Adult Females ◽  
Coniferous Plantation ◽  
The Mean

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

Population dynamics of the black-cheeked gnateater (Conopophaga melanops, Conopophagidae) in southern Brazil

2009 ◽  
Vol 25 (6) ◽  
pp. 605-613 ◽  
Author(s):  
André Magnani Xavier de Lima ◽  
James Joseph Roper
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Breeding Season ◽  
Survival Rates ◽  
Territory Size ◽  
Adult Survival ◽  
Southern Brazil ◽  
Annual Survival ◽  
Socially Monogamous ◽  
Population Structure And Dynamics

Abstract:Population structure and dynamics of the black-cheeked gnateater (Conopophaga melanops) were studied at Salto Morato Nature Reserve, in Paraná, southern Brazil, from October 2006 to September 2007. Territory size and population density, breeding season (timing and length), reproductive success and annual survival rates were estimated from sightings of 18 marked adult birds and the success of 18 nesting attempts. The black-cheeked gnateater is socially monogamous and territorial, with a breeding-season length of approximately 3 mo beginning in early October. Predation caused most nest failures, nest survival was 0.96 d−1and apparent annual nesting success was 22%, resulting in annual productivity of 0.36 individuals per adult. Apparent adult annual survival was ~0.44 y−1. Seventy-five per cent of fledglings survived at least 2 mo after fledging. Two methods of estimating population growth rate suggest very different rates: r = −0.04 (~ stable), or λ varies between 0.475–0.616 (declining). Yet, low apparent adult survival suggests that territories are not permanent, perhaps abandoned after nest failure. We find that by estimating population growth, even in short-term studies, testable hypotheses can be generated that will allow better understanding of population dynamics.

scholarly journals Timing outweighs amount of rainfall in shaping population dynamics

2020 ◽  
Author(s):  
Guoliang Li ◽  
Xinrong Wan ◽  
Baofa Yin ◽  
Wanhong Wei ◽  
Xianglei Hou ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Population Size ◽  
Vole Population ◽  
Bottom Up ◽  
Manipulative Experiments ◽  
Arid Steppe ◽  
Steppe Grassland ◽  
Lasiopodomys Brandtii ◽  
Manipulation Experiment

Abstract Climate variability has been widely documented to have bottom-up effects on the population dynamics of animals1,2, but the mechanisms underlying these effects have been rarely investigated through field manipulative experiments that control for confounding factors3. Here, we examined the effects of different rainfall patterns (i.e. timing and amount) on the population size of Brandt’s voles Lasiopodomys brandtii in semi-arid steppe grassland in Inner-Mongolia by conducting a 10-year (2010-2019) rainfall manipulation experiment in twelve 0.48 ha field enclosures. We found that moderate rainfall increase during the early rather than late growing season drove marked increases in population size through increasing the biomass of preferred plant species, whereas heavily increased rainfall produced no further increase in vole population growth. The increase in vole population size was more coupled with increased reproduction of overwintered voles and increased body mass of young-of-year than with better survival. Our results provide the first experimental evidence for the bottom-up effects of changing rainfall on the population growth of small mammals, and highlight the importance of rainfall timing on the population dynamics of wildlife in the steppe grassland environment.

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