The quantitative study of marked individuals in ecology, evolution ...

EURING 2003 Radolfzell
We found two breeding strategies which have the same fitness, characterized by the
number of years without reproduction (2 or 3) and the number of clutches within reproductive
years. However, such strategies are not fixed for a given female.
10:45 AM - 11:05 AM
Modelling senility and dispersal of Red deer
Ted Catchpole, T.N. Coulson, Y. Fan, & B.J.T. Morgan
Red deer (Cervus elaphus) on the island of Rum have been closely studied for many
years. In particular, this has resulted in an extensive mark-recapture-recovery (mrr)
data set. Models for these data need an elaborate age-structure for survival, because
deer react differently to environmental factors at different stages of their lives. An additional
interesting feature of the data is that animals may leave the study area. Thus
we are interested not only in modelling deer survival, but also deer dispersal. Our
modeling approach is a classical statistical one. The two sexes need to be considered
separately. Within each sex, we use standard likelihood tools and information criteria
to identify age-classes, separately for survival and dispersal. Within each age-class,
the relevant probability does not vary over the ages desribed by that class, with the
exception of the oldest age-class for survival. This then allows us to undertake logistic
regressions of the relevant age-class probabilities on a mixture of environmental and
individual covariates. Senility, a gradual decline in survival probability with age, is described
by means of a logistic regression on age within the oldest survival ageclasses
for males and females. The final models that we select for males and for females
have an attractive simplicity. They demostrate clearly the differences that exist
between males and females, and may be used for predicting future behaviour, and
the effects of alternative management policies.
The work of this paper is a natural extension of the models and model-selection
procedures that have been developed for Soay sheep (Ovis aries) in Catchpole et al
(2000) and Coulson et al (2001). The present work builds on the modelling of male
red-deer alone by Catchpole et al (2002), and the modelling of both sexes in Fan et al
(2002).
11:05-11:25 AM
Assessing senescence patterns in populations of large mammals
Jean-Michel Gaillard & Anne Viallefont
Theoretical models such as Gompertz and Weibull models are commonly used to
study senescence in survival for humans (Olshansky & Carnes 1997) and laboratory
or captive animals (Ricklefs 2000) for which a complete follow up of individuals is
available. For wild populations of vertebrates, senescence in survival has more commonly
been assessed by fitting simple linear or quadratic relationships between survival
and age (e. g., McDonald et al. 1996, Newton and Rothery 1997, Nichols et al.
1997, Loison et al. 1999). By using appropriate constraints on survival parameters in
Capture-Mark-Recapture (CMR) models, we propose a first analysis of the suitability
of Gompertz and Weibull models for describing aging-related mortality in free-ranging
populations of ungulates. We first show how to handle Gompertz and Weibull models
in the context of CMR analyses. Then we perform a comparative analysis of senescence
patterns in both sexes of two ungulate species highly contrasted according
to the intensity of sexual selection. Evolutionary implications of our results are
discussed.
9