DOI: 10.5061/dryad.fn2z34tsq
title: Modeling the demography of species providing extended parental care: A capture-recapture approach with a case study on Polar Bears (Ursus maritimus)

description: 1. In species providing extended parental care, one or both parents care
 for altricial young over a period including more than one breeding season.
 We expect large parental investment and long-term dependency within family
 units to cause high variability in life trajectories among individuals
 with complex consequences at the population level. So far, models for
 estimating demographic parameters in free-ranging animal populations
 mostly ignore extended parental care, thereby limiting our understanding
 of its consequences on parents and offspring life histories. 2. We
 designed a capture-recapture multi-event model for studying the demography
 of species providing extended parental care. It handles statistical
 multiple-year dependency among individual demographic parameters grouped
 within family units, variable litter size, and uncertainty on the timing
 at offspring independence. It allows for the evaluation of trade-offs
 among demographic parameters, the influence of past reproductive history
 on the caring parent’s survival status, breeding probability and litter
 size probability, while accounting for imperfect detection of family
 units. We assess the model performance using simulated data, and
 illustrate its use with a long-term dataset collected on the Svalbard
 polar bears (Ursus maritimus). 3. Our model performed well in terms of
 bias and mean square error and in estimating demographic parameters in all
 simulated scenarios, both when offspring departure probability from the
 family unit occurred at a constant rate or varied during the field season
 depending on the date of capture. For the polar bear case study,
 we provide estimates of adult and dependent offspring survival rates,
 breeding probability and litter size probability. Results showed that the
 outcome of the previous reproduction influenced breeding probability. 4.
 Overall, our results show the importance of accounting for i) the
 multiple-year statistical dependency within family units, ii) uncertainty
 on the timing at offspring independence, and iii) past reproductive
 history of the caring parent. If ignored, estimates obtained for breeding
 probability, litter size, and survival can be biased. This is of interest
 in terms of conservation because species providing extended parental care
 are often long-living mammals vulnerable or threatened with extinction.
description: Polar bears were caught and individually marked as part of a
 long-term monitoring program on the ecology of polar bears in the Barents
 Sea region (Derocher 2005). All bears one year or older were immobilized
 by remote injection of a dart (Palmer Cap-Chur Equipment, Douglasville,
 GA, USA) with the drug Zoletil® (Virbac, Carros, France) (Stirling et al.
 1989). The dart was fired from a small helicopter (Eurocopter 350 B2 or
 B3), usually from a distance of about 4 to 10 meters. Cubs of the year
 were immobilized by injection with a syringe. Cubs and yearlings were
 highly dependent on their mother; therefore, they remained in her vicinity
 and were captured together with their mother.  The file
 "CR.txt" contains the capture-histories of n= 158 family units
 captured between 1992 to 2019 arranged in a matrix with the status of each
 family unit (in rows) provided each year (in columns). Code 1 is for
 two-year-old independent juvenile female, code 2 is three-year-old
 independent juvenile female, code 3 is four-year-old subadult female, code
 4 is four-year-old subadult female, code 5 is adult female with one
 cub, code 6 is adult female with two cubs, code 7 is adult female with one
 yearling, code 8 is adult female with two yearlings, code 9 is adult
 female with one depdendent two-year-old bear, code 10 is adult female with
 two dependent two-year-old bears, code 11 is adult female without
 dependent offspring, code 0 means a no-capture event. 
 The file "captureday.txt" contains the date of capture,
 in day of the year, for each family unit (in row) each year (in column).
 "NA" means a no-capture event.  The file
 "weaning.txt" contains the status (code 1 is independent from
 its mother, code 0 means still dependent from its mother), identification
 number and date of capture of each two-year-old bear (n=120 males and
 females) captured on the field.
description: R script with guidance to analyse these data is provided at
 https://github.com/SCubaynes/Appendix2_extendedparentalcare