Apparent demographic changes in black-tailed deer associated with wolf control on northern Vancouver Island

1994 ◽  
Vol 72 (5) ◽  
pp. 878-884 ◽  
Author(s):  
Ian W. Hatter ◽  
Doug W. Janz
Keyword(s):  
Population Change ◽  
Survival Rates ◽  
Vancouver Island ◽  
Adult Mortality ◽  
Recruitment Rate ◽  
Sensitivity Analyses ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Demographic Changes ◽  
Odocoileus Hemionus Columbianus

A simple difference equation model was used to provide a perspective on demographic changes in a Columbian black-tailed deer (Odocoileus hemionus columbianus) population prior to and during wolf (Canis lupus) control on northern Vancouver Island. The model reconstructed spring (pre-fawning) deer numbers and adult survival rates from an annual abundance index, the proportion of the population consisting of juveniles 10–11 months of age, and hunter harvest. The actual (λ) and potential (λp, in the absence of hunting) rates of deer population change, adult nonhunting survival (Sn), adult hunting mortality (Mh) and recruitment (R) rates were estimated for three growth periods: (1) predecline (1970–1976), wolf numbers low but increasing, λ = 1.02, λp = 1.13, Sn = 0.90, Mh = 0.09, R = 0.22; (2) decline (1976–1983), wolves abundant, λ = 0.81, λp = 0.85, Sn = 0.76, Mh = 0.05, R = 0.09; and (3) recovery (1983–1990), wolves reduced, λ = 1.17, λp = 1.24, Sn = 0.94, Mh = 0.03, R = 0.23. The recruitment (Rs) required to balance adult mortality (λ = 1.00) was ~16%. Sensitivity analyses using plausible extremes in demographic rates suggested that changes in juvenile survival had the greatest impact on recruitment. Rate of population change appeared to be most sensitive to juvenile survival and adult nonhunting survival.

Juvenile survival and recruitment in a population of Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica

1987 ◽  
Vol 65 (12) ◽  
pp. 2993-2997 ◽  
Author(s):  
J. Ward Testa
Keyword(s):  
Census Data ◽  
Survival Rates ◽  
Breeding Population ◽  
Weddell Seal ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Apparent Survival ◽  
Mcmurdo Sound ◽  
Juvenile Dispersal ◽  
Weddell Seals

Survival and recruitment of Weddell seal pups were studied in eastern McMurdo Sound, Antarctica. Pups were marked and their apparent survival estimated by mark–recapture methods. The resulting estimates were used together with published estimates of adult survival, yearly sighting probabilities, and direct counts of pup production to simulate the dynamics of the population and evaluate the assumption that it is closed to immigration. Estimates derived from census data in 1982 and 1983 were over five times larger than those simulated. This discrepancy was due to the extremely low juvenile survival rates calculated from marked seals. Since few animals born in Erebus Bay return to breed, the large adult breeding population must be the result of substantial immigration, indicating an important role for juvenile dispersal in the population dynamics of Weddell seals.

scholarly journals Cyclic dynamics of snowshoe hares on a small island in the Yukon

2002 ◽  
Vol 80 (8) ◽  
pp. 1442-1450 ◽  
Author(s):  
Charles J Krebs ◽  
Todd N Zimmerling ◽  
Claire Jardine ◽  
Kim A Trostel ◽  
Alice J Kenney ◽  
...  
Keyword(s):  
Population Decline ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Adult Survival ◽  
Small Island ◽  
Juvenile Survival ◽  
Lower Amplitude ◽  
Arctic Ground Squirrels ◽  
Reproductive Rates ◽  
Survival Differences

Snowshoe hare (Lepus americanus) populations were monitored from 1977 to 2001 on Jacquot Island (5 km2) in Kluane Lake, southwestern Yukon, and on nearby mainland sites. Jacquot Island hares averaged twice the density of mainland control populations and, although they show 10-year cycles, fluctuate with much lower amplitude than mainland populations. Three separate intensive studies over 6 years attempted to determine what caused these differences. We tested two hypotheses to explain the dynamics. Reproductive rates of hares were similar on Jacquot Island and the mainland. Adult survival rates were higher on the island in most years, with the exception of years of population decline. Juvenile survival rates from 0 to 30 days of life were much higher on the island than on the mainland except for decline summers. The adult- and juvenile-survival differences between the island and the mainland were explained most consistently by predation. Improved survival on the island is correlated with a reduction in the numbers and types of predators found on Jacquot Island compared with the mainland. In particular, red squirrels were rare on Jacquot Island, arctic ground squirrels were absent, and the larger predators, like lynx and great-horned owls, were sporadic in occurrence on this small island.

Demography of a yellow-footed rock-wallaby Petrogale xanthopus colony in the threatened New South Wales sub-population.

2006 ◽  
Vol 28 (2) ◽  
pp. 215 ◽  
Author(s):  
A. Sharp ◽  
M. Norton ◽  
A. Marks
Keyword(s):  
New South ◽  
New South Wales ◽  
Survival Rates ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Management Actions ◽  
South Wales ◽  
Low Levels ◽  
Reproductive Rates ◽  
Substantial Decline

The remnant New South Wales (NSW) yellow-footed rock-wallaby (Petrogale xanthopus) population underwent a substantial decline between 1985 and 1992 and remained at dangerously low levels until 1995. To determine the processes underlying this decline, a population study was conducted at one colony, between winter 1995 and winter 1998. The colony was observed to remain relatively constant in size, consisting of between 12 or 13 individuals throughout the study. Reproductive rates were found to be relatively high. Both reproduction and pouch young survival were comparable with those reported for other P. xanthopus colonies, while adult survival rates were higher than those noted in other studies. Because population size remained constant during the study and adult survivorship was consistently high, this suggested that juvenile recruitment into the colony was low. Such low levels of recruitment may have had a substantive role in the slow decline of the entire NSW P. xanthopus population. The results of this study suggest that any management actions undertaken in the NSW P. xanthopus population should focus on increasing juvenile survival rates. Further research is required to determine whether juvenile survival is constrained by predation or competition with other herbivores.

Estimation of juvenile survival, adult survival, and age-specific pupping probabilities for the female grey seal (Halichoerus gryprus) on Sable Island from capture-recapture data

2000 ◽  
Vol 57 (1) ◽  
pp. 247-253 ◽  
Author(s):  
Carl J Schwarz ◽  
Wayne T Stobo
Keyword(s):  
Survival Rate ◽  
Survival Rates ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Grey Seal ◽  
Capture Recapture ◽  
Adult Survival Rate

We use a longitudinal capture-recapture study from resightings of grey seals (Halichoerus gryprus) branded as young on Sable Island to estimate (i) the juvenile survival rate from the time of branding to age 4, (ii) the yearly adult survival rate from age 4 to age 9, and (iii) the age-specific pupping probabilities, i.e., the probability that a seal will first give birth at each age. The estimated juvenile survival rate from branding (just after weaning) to age 4 ranged from 70 to 80%; however, the lower values are known to be biased low because the study was terminated early. The estimated yearly adult survival rates for ages 4-9 ranged from 0.88 to 0.92·year-1. The estimated probabilities of first giving birth to a young seal (pupping) at ages 4-9 are 0.28, 0.41, 0.18, 0.06, 0.05, and 0.02, respectively, and the estimated average age of first pupping is 5.2 years.

Ocean survival and exploitation of coho salmon (Oncorhynchus kisutch) stocks from the east coast of Vancouver Island, British Columbia

1997 ◽  
Vol 54 (7) ◽  
pp. 1433-1449 ◽  
Author(s):  
M Labelle ◽  
C J Walters ◽  
B Riddell
Keyword(s):  
Linear Models ◽  
East Coast ◽  
Coho Salmon ◽  
Survival Rates ◽  
Oncorhynchus Kisutch ◽  
Vancouver Island ◽  
Adult Survival ◽  
Stock Type ◽  
High Level ◽  
Log Linear

Juvenile tagging and escapement enumeration was conducted during 1985-1988 in nine streams within a 150-km section on the east coast of Vancouver Island. Fourteen coho salmon (Oncorhynchus kisutch) stocks of wild, hatchery, and mixed origin were monitored for ocean survival and exploitation patterns. Estimates of smolt-to-adult survival ranged from 0.5 to 23.1%. Survival rates were highly variable across years and stocks. No stock or stock type had consistently higher survival, but one hatchery stock exhibited consistently lower survival. Average exploitation rates were about 80% each year, and were as high as 96% for some stocks. Exploitation rates were not consistently higher or lower for any stock or stock type, but hatchery reared coho tended to be subject to higher exploitation. Log-linear models were used to assess the effects of various factors on survival and exploitation. Certain hatchery rearing practices had a large influence on survival. Genetic factors, run timing, and stream location had large influences on exploitation rates. An assessment of covariation in survival and exploitation rates showed no indication of a high level of similarity among stocks from adjacent streams or among stock types in this region.

scholarly journals Constructing a coherent joint prior while respecting biological realism: application to marine mammal stock assessments

2007 ◽  
Vol 64 (6) ◽  
pp. 1085-1100 ◽  
Author(s):  
John R. Brandon ◽  
Jeffrey M. Breiwick ◽  
André E. Punt ◽  
Paul R. Wade
Keyword(s):  
Marine Mammal ◽  
Prior Distribution ◽  
Survival Rates ◽  
Estimation Methods ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Functional Relationships ◽  
Stock Assessments ◽  
Biological Realism ◽  
Parameter Values

Abstract Brandon, J. R., Breiwick, J. M., Punt, A. E., and Wade, P. R. 2007. Constructing a coherent joint prior while respecting biological realism: application to marine mammal stock assessments. – ICES Journal of Marine Science, 64: 1085–1100. Bayesian estimation methods, employing the Sampling–Importance–Resampling algorithm, are currently used to perform stock assessments for several stocks of marine mammals, including the Bering–Chukchi–Beaufort Seas stock of bowhead whales (Balaena mysticetus) and walrus (Odobenus rosmarus rosmarus) off Greenland. However, owing to the functional relationships among parameters in deterministic age-structured population dynamics models, placing explicit priors on each life history parameter in addition to the population growth rate parameter results in an incoherent joint prior distribution (i.e. two different priors on the estimated parameters). One solution to constructing a coherent joint prior is to solve for juvenile survival analytically, using values generated from the prior distributions for the remaining parameters. However, certain combinations of model parameter values result in values for juvenile survival that are larger than adult survival, which is biologically implausible. Therefore, to respect biological realism, certain parameter values must be rejected for some or all the remaining parameters. This study investigates several alternative resampling schemes for obtaining a realistic joint prior distribution, given the constraint on survival rates. The sensitivity of assessment results is investigated for data-rich (bowhead) and data-poor (walrus) scenarios. The results based on limited data are especially sensitive to the choice of alternative resampling scheme.

Persistence of giants: population dynamics of the limpet Scutellastra laticostata on rocky shores in Western Australia

2020 ◽  
Vol 646 ◽  
pp. 79-92
Author(s):  
RE Scheibling ◽  
R Black
Keyword(s):  
Population Dynamics ◽  
Western Australia ◽  
Size Structure ◽  
Survival Rates ◽  
Maximum Size ◽  
High Rate ◽  
Adult Survival ◽  
Rocky Shores ◽  
Adult Size ◽  
Decadal Time Scale

Population dynamics and life history traits of the ‘giant’ limpet Scutellastra laticostata on intertidal limestone platforms at Rottnest Island, Western Australia, were recorded by interannual (January/February) monitoring of limpet density and size structure, and relocation of marked individuals, at 3 locations over periods of 13-16 yr between 1993 and 2020. Limpet densities ranged from 4 to 9 ind. m-2 on wave-swept seaward margins of platforms at 2 locations and on a rocky notch at the landward margin of the platform at a third. Juvenile recruits (25-55 mm shell length) were present each year, usually at low densities (<1 m-2), but localized pulses of recruitment occurred in some years. Annual survival rates of marked limpets varied among sites and cohorts, ranging from 0.42 yr-1 at the notch to 0.79 and 0.87 yr-1 on the platforms. A mass mortality of limpets on the platforms occurred in 2003, likely mediated by thermal stress during daytime low tides, coincident with high air temperatures and calm seas. Juveniles grew rapidly to adult size within 2 yr. Asymptotic size (L∞, von Bertalanffy growth model) ranged from 89 to 97 mm, and maximum size from 100 to 113 mm, on platforms. Growth rate and maximum size were lower on the notch. Our empirical observations and simulation models suggest that these populations are relatively stable on a decadal time scale. The frequency and magnitude of recruitment pulses and high rate of adult survival provide considerable inertia, enabling persistence of these populations in the face of sporadic climatic extremes.

scholarly journals Warming Arctic summers unlikely to increase productivity of shorebirds through renesting

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sarah T. Saalfeld ◽  
Brooke L. Hill ◽  
Christine M. Hunter ◽  
Charles J. Frost ◽  
Richard B. Lanctot
Keyword(s):  
Climate Change ◽  
Survival Rates ◽  
The Arctic ◽  
Adult Survival ◽  
Chick Survival ◽  
Ecological Processes ◽  
Bird Populations ◽  
Phenological Mismatch ◽  
Daily Survival ◽  
Adequate Food

AbstractClimate change in the Arctic is leading to earlier summers, creating a phenological mismatch between the hatching of insectivorous birds and the availability of their invertebrate prey. While phenological mismatch would presumably lower the survival of chicks, climate change is also leading to longer, warmer summers that may increase the annual productivity of birds by allowing adults to lay nests over a longer period of time, replace more nests that fail, and provide physiological relief to chicks (i.e., warmer temperatures that reduce thermoregulatory costs). However, there is little information on how these competing ecological processes will ultimately impact the demography of bird populations. In 2008 and 2009, we investigated the survival of chicks from initial and experimentally-induced replacement nests of arcticola Dunlin (Calidris alpina) breeding near Utqiaġvik, Alaska. We monitored survival of 66 broods from 41 initial and 25 replacement nests. Based on the average hatch date of each group, chick survival (up to age 15 days) from replacement nests (Ŝi = 0.10; 95% CI = 0.02–0.22) was substantially lower than initial nests (Ŝi = 0.67; 95% CI = 0.48–0.81). Daily survival rates were greater for older chicks, chicks from earlier-laid clutches, and during periods of greater invertebrate availability. As temperature was less important to daily survival rates of shorebird chicks than invertebrate availability, our results indicate that any physiological relief experienced by chicks will likely be overshadowed by the need for adequate food. Furthermore, the processes creating a phenological mismatch between hatching of shorebird young and invertebrate emergence ensures that warmer, longer breeding seasons will not translate into abundant food throughout the longer summers. Thus, despite having a greater opportunity to nest later (and potentially replace nests), young from these late-hatching broods will likely not have sufficient food to survive. Collectively, these results indicate that warmer, longer summers in the Arctic are unlikely to increase annual recruitment rates, and thus unable to compensate for low adult survival, which is typically limited by factors away from the Arctic-breeding grounds.

Wolf predation in a multiple-ungulate system in northern British Columbia

1998 ◽  
Vol 76 (8) ◽  
pp. 1551-1569 ◽  
Author(s):  
A T Bergerud ◽  
J P Elliott
Keyword(s):  
British Columbia ◽  
Canis Lupus ◽  
Birth Rate ◽  
Rangifer Tarandus ◽  
Adult Mortality ◽  
Recruitment Rate ◽  
Wolf Predation ◽  
Rate Of Increase ◽  
Ovis Dalli ◽  
Hunting Statistics

Caribou (Rangifer tarandus), elk (Cervus canadensis), moose (Alces alces), and Stone's sheep (Ovis dalli stonei) were either decreasing or stable in numbers in two areas in northeastern British Columbia in 1981-1982, prior to reductions in wolf (Canis lupus) numbers. Following the reduction of wolf numbers, recruitment improved 2-5 times for all four species, and all populations increased, based on either hunting statistics, census results, and (or) recruitments greater than 24 offspring at 9 months of age per 100 females. Recruitment of offspring at 9 months of age, when regressed against wolf numbers, declined with decelerating slopes for all four species. This inverse functional response is hypothesized to result from the preparturient spacing of females to reduce predation risk, and in this regard moose seem the least secure and sheep the most effectively spaced. For the four species, mean recruitment at 9 months of age that balanced adult mortality and provided a finite rate of increase of 1.00 was 24.16 ± 0.91 offspring/100 females (n = 11, coefficient of variation = 12.5%). The predicted recruitment rate for all four species in the absence of wolves was 53-57 offspring/100 females. But the birth rate of moose was much higher than those of the other species, indicating greater loss to other factors of which bear predation may be the greatest. Following wolf reductions of 60-86% of entire travelling packs, the wolves quickly recolonized the removal zones, with rates of increase ranging from 1.5 to 5.6.

scholarly journals Fitness of breeders in social Damaraland mole-rats is independent of group size

2021 ◽  
Author(s):  
Jack Thorley ◽  
Hanna Bensch ◽  
Kyle Finn ◽  
Tim Clutton-Brock ◽  
Markus Zöttl
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Survival Rates ◽  
Group Living ◽  
Adult Survival ◽  
High Survival ◽  
Successful Reproduction ◽  
Related Group ◽  
Group Members ◽  
Using Data

Damaraland mole-rats (Fukomys damarensis) are usually viewed as an obligatorily group living eusocial species in which successful reproduction is dependent on reproductive altruism of closely related group members. However, the reproductive ecology of social mole-rats in their natural environment remains poorly understood and it is unclear to what extent successful reproduction is dependent on assistance from other group members. Using data from a 7-year field study of marked individuals, we show that, after dispersal from their natal group, individuals typically settled alone in new burrow systems where they enjoyed high survival rates, and often remained in good body condition for several years before finding a mate. Unlike most other eusocial or singular cooperative breeders, we found that Damaraland mole-rats reproduced successfully in pairs without helpers and experimentally formed pairs had the same reproductive success as larger established groups. Overall there was only a weak increase in reproductive success with increasing group size and no effect of group size on adult survival rates across the population. Juveniles in large groups grew faster early in life but their growth rates declined subsequently so that they eventually plateaued at a lower maximum body mass than juveniles from small groups. Taken together, our data suggest that the fitness benefits of group living to breeders are small and we suggest that extended philopatry in Damaraland mole-rats has evolved because of the high costs and constraints of dispersal rather than because of strong indirect benefits accrued through cooperative behaviour.

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