Data from: Variations in age- and sex-specific survival rates help explain population trend in a discrete marine mammal population

Civil, Mònica Arso1; Cheney, Barbara2; Quick, Nicola J.3, 1; Islas-Villanueva, Valentina1, 4; Graves, Jeff A.1; Janik, Vincent M.1; Thompson, Paul M.2; Hammond, Phillip S.1

Published Dec 19, 2018 on Dryad. https://doi.org/10.5061/dryad.8qm8r4m

Data files

Dec 19, 2018 version files 57.57 KB

Adult only_Robust design models.txt

19.98 KB
calf_age CJS models.txt

1.85 KB
JuvAd_Multistate models.txt

6.56 KB
JuvAd_Robust design models.txt

27.88 KB
time_intervals.txt

1.31 KB

Abstract

1. Understanding the drivers underlying fluctuations in the size of animal populations is central to ecology, conservation biology and wildlife management. Reliable estimates of survival probabilities are key to population viability assessments, and patterns of variation in survival can help inferring the causal factors behind detected changes in population size. 2. We investigated whether variation in age and sex-specific survival probabilities could help explain the increasing trend in population size detected in a small, discrete population of bottlenose dolphins Tursiops truncatus off the east coast of Scotland. 3. To estimate annual survival probabilities we applied capture-recapture models to photo-identification data collected from 1989 to 2015. We used robust design models accounting for temporary emigration to estimate juvenile and adult survival, multi-state models to estimate sex-specific survival, and age-models to estimate calf survival. 4. We found strong support for an increase in juvenile/adult annual survival from 93.1% to 96.0% over the study period, most likely caused by a change in juvenile survival. Examination of sex-specific variation showed weaker support for this trend being a result of increasing female survival, which was overall higher than for males and animals of unknown sex. Calf survival was lower in the first than second year; a bias in estimating third-year survival will likely exist in similar studies. There was some support first-born calf survival being lower than for calves born subsequently. 5. Coastal marine mammal populations are subject to the impacts of environmental change, increasing anthropogenic disturbance and the effects of management measures. Survival estimates are essential to improve our understanding of population dynamics and help predict how future pressures may impact populations, but obtaining robust information on the life history of long-lived species is challenging. Our study illustrates how knowledge of survival can be increased by applying a robust analytical framework to photo-identification data.

Usage notes

Sighting histories_juveniles&adults_Robust Design models

This file contains the monthly sighting histories of 205 marked juvenile and adult bottlenose dolphins sighted off the east coast of Scotland between 1989 and 2015, and used to estimate survival rate using a robust design modelling framework. The file can be imported into RMark, and then converted to an .inp file to fit mark-recapture models (using MARK software). Time intervals (i.e. primary and secondary occasions) for robust design analysis are given in the file "time.intervals.txt"

JuvAd_Robust design models.txt

Sighting histories_Sex-specific Juveniles&Adults_Multistate models

This file contains the annual sighting histories of 205 marked juvenile and adult bottlenose dolphins sighted off the east coast of Scotland between 1989 and 2015, used to estimate sex-specific survival rates using multi-state models. Information on sex is provided so that U=unknown, M=male and F=female, 0=not sighted. The file can be imported into RMark, and then converted to an .inp file to fit mark-recapture models (using MARK software).

JuvAd_Multistate models.txt

Sighting histories_calf_age CJS models

This file contains the annual sighting histories of 56 bottlenose dolphin calves sighted off the east coast of Scotland between 1990 and 2015, and used to estimate age specific survival rates up to 3 years of age. The sighting histories are restricted to calves whose mothers were seen in the three years following birth. The file can be imported into RMark, and then converted to an .inp file to fit mark-recapture models (using MARK software) .

calf_age CJS models.txt

Sighting histories_adults only_Robust Design models

This file contains a restricted dataset of only adult bottlenose dolphins, sighted off the east coast of Scotland between 1989 and 2015. The monthly sighting histories were used to investigate if the detected trend in juvenile&adult survival was more likely a change in adult or juvenile survival. The file can be imported into RMark, and then converted to an .inp file to fit mark-recapture models (using MARK software). Time intervals (i.e. primary and secondary occasions) for robust design analysis are given in the file "time.intervals.txt"

Adult only_Robust design models.txt

Time intervals for Robust Design models

This file contains the time intervals (primary and secondary occasions) defined for the datasets JuvAd_Robust design models.txt and Adult only_Robust design models.txt. These time intervals are defined to use in RMark package when fitting mark-recapture models.

time_intervals.txt