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Dryad

Post-weaning survival in kangaroos is high and constant until senescence: Implications for population dynamics

Cite this dataset

Bergeron, Rachel et al. (2022). Post-weaning survival in kangaroos is high and constant until senescence: Implications for population dynamics [Dataset]. Dryad. https://doi.org/10.5061/dryad.dv41ns21w

Abstract

Large herbivores typically have consistently high prime-aged adult survival and lower, more variable, juvenile and senescent survival. Many kangaroo populations undergo greater fluctuations in density than other large herbivores, but age- and sex-specific survival of kangaroos and their response to environmental variation remain poorly estimated. We used long-term capture-mark-recapture data on 920 individuals to investigate the survival component of eastern grey kangaroo (Macropus giganteus) population dynamics. Forage availability and population density were monitored quarterly and included as predictors of survival in Bayesian Cormack-Jolly-Seber models. Annual survival probabilities were estimated for 5 age classes: 0 years (juveniles), 1–2 years (sub-adults), 3–6 years (prime-aged adults), 7–9 years (pre-senescent adults), and ≥10 years (senescent adults). Survival of juveniles varied widely during our 12-year study, ranging from 0.07–0.90 for females and 0.05–0.92 for males. Sub-adult survival was 0.80–0.93 for females and 0.75–0.85 for males, while that of prime-aged adults was ≥0.94 for females and ≥0.83 for males, despite large fluctuations in forage and density. The survival of pre-senescent adults spanned 0.86–0.93 for females and 0.60–0.86 for males. Senescent survival was variable, at 0.49–0.90 for females and 0.49–0.80 for males. Male survival was significantly lower than female survival in prime-aged and pre-senescent adults, but not in other age classes. Although most models supported by WAIC selection included one or a combination of environmental covariates, none of these individual covariates had a discernable effect on survival. Temporal variability in overall survival was mostly due to changes in survival of juvenile and senescent kangaroos. Kangaroo survival patterns are similar to those of ungulates, suggesting a strong role of sex-age structure on population dynamics.

Methods

Descriptions of the methods used to collect, prepare, and analyse the data are in Bergeron et al.: Post-weaning survival in kangaroos is high and constant until survival: implications for population dynamics.

Individual IDs have been replaced by randomised numbers.

Usage notes

Observation history

Each row represents an individual, and each column represents a year, from 2008 to 2020.

Represents the observation process of the Cormack-Jolly-Seber model used to estimate apparent survival. Denotes whether an individual was observed during the annual August-November field season or not. 0 = individual was not observed on the study area, 1 = individual was observed on the study area.

obsF.csv contains female data, obsM.csv contains male data.

State

Each row represents an individual, and each column represents a year, from 2008 to 2020.

Represents the state process of the Cormack-Jolly-Seber model used to estimate apparent survival. Denotes whether an individual was truly alive in a given year or not. 0 = individual has been found dead and is therefore certainly not alive, 1 = individual was observed this year or in a later year and is therefore necessarily alive, NA = individual was not observed, state is therefore not known with certainty.

stateF.csv contains female data, stateM.csv contains male data.

Age

Each row represents an individual, and each column represents a year, from 2008 to 2020.

Denotes each individual's age in a given year, starting in the year it was first captured, from 0 to 28. For computational efficiency, age was always entered until the last year of the study, whether an individual was still alive or not. Age hence spans 0-28 here, although no individual has lived longer than 21 years throughout the duration of the study. Rows of all NAs represent individuals which were first caught as adult and are therefore of unknown age.

ageF.csv contains female data, ageM.csv contains male data.

ID

ID: each represents an individual kangaroo.

first: represents the time step at which a given individual was first captured, from 2008 to 2020. 1 = 2008, 2 = 2009, and so forth, until 13 = 2020.

last: represents the time step at which an individual was last potentially alive, from 2008 to 2020. For any individual that disappeared but was never found dead, or for any individual that died of anthropogenic causes (mostly vehicle collisions or illegal shooting), this would be the last year of the study. 1 = 2008, 2 = 2009, and so forth, until 13 = 2020.

idF.csv contains female data, idM.csv contains male data.

Environmental data

Year: from 2008 to 2020.

Dens and DensSD: population density in kangaroos/ha and associated standard deviation, from distance sampling model.

Veg and VegSD: mean total palatable forage grown from October 1 of the previous year to September 30 of the current year in g/m2 and associated standard deviation.

resDens and resDensSD: residual density and associated standard deviation obtained by sequential regression of population density in kangaroo/ha on total forage in g/m2.

env.csv contains environmental data throughout the period over which survival is estimated, envLag.csv contains environmental data lagging the survival period by 6 months.

Nimble code

Script used to assemble Nimble data and run Cormack-Jolly-Seber models to estimate apparent survival while accounting for imperfect detection.

Roo_NimbleCode.R

 

See Bergeron et al. for more details.

Funding

Natural Sciences and Engineering Research Council