Tesis:
Biological basis for wild ungulate management: factors associated with body weight and reproductive traits
- Autor: MARTINEZ JAUREGUI, María
- Título: Biological basis for wild ungulate management: factors associated with body weight and reproductive traits
- Fecha: 2007
- Materia: Sin materia definida
- Escuela: E.T.S. DE INGENIEROS DE MONTES
- Departamentos: SILVOPASCICULTURA
- Acceso electrónico:
- Director/a 1º: SAN MIGUEL AYANZ, Alfonso
- Director/a 2º: COULSON, Tim
- Resumen: Ungulates have become a major component of many different ecological systems. They are currently of enormous socio-economic and environmental importance throughout Europe. Therefore complete management plans are essential and need to consider the complexity of elements and interactions which affect the wild ungulate ecosystems. For this reason, in order to identify optimal strategies for the management and conservation of wild populations and their ecosystems, it is now crucial to understand the biological, ecological, evolutionary and socio-economic factors that influence such ungulate populations. In this thesis, the general objective is to provide new information on wild ungulate population dynamics, the environment influence in their ecology and the evolutionary consequences of individual success and, therefore, to enable optimal strategies for the management and conservation of wild ungulate populations to be identified. Particularly, we focus on three main complementary y topics in this thesis. TOPIC 1: Hunting strategies, population structure and body weight of male red deer. Much insight can be derived from records of shot animals. Most researchers using such data assume that their data represents a random sample of a particular demographic class. However, hunters typically select a non-random subset of the population and hunting is, therefore, not a random process. Here, with red deer hunting data from a ranch in Toledo, Spain, we demonstrate that data collection methods have a significant influence upon the apparent relationship between age and weight. We argue that a failure to correct for such methodological bias may have significant consequences for the interpretation of analyses involving weight or correlated traits such as breeding success and urge researchers to explore methods to identify and correct for such bias in their data. We also support with body weight data of male red deer that other factors in addition to natural selection affect these managed populations depending on the hunting strategy used in a Mediterranean socio-economic context. TOPIC 2: Body weight and its relationship with environmental conditions. There are multiple paths via which environmental variation can impact herbivore ecology and this makes the identification of the drivers difficult. Researchers have used diverse approaches to describe the association between environmental variation and ecology, including local weather, large scale patterns of weather (such as NAO) and satellite imagery reflecting plant productivity/phenology (for example: NDVI). However, it is unclear to what extent it is possible to find a single measure that captures climatic effects over broad spatial scales. There may, in fact be no a priori reason to expect populations of the same species living in different areas to respond in the same way to climate as their population may experience limiting factors at different times of the year, and the form of regulation may differ between populations. Here we examine whether the same environmental indices influence body weight in populations of female red deer living in Mediterranean Spain, Western Scotland, and Norway. We found substantial differences in the pattern of weight change over time in adult female red deer between study areas as well as different environmental drivers associated with variation in weight. The lack of general patterns for a given species at a continental scale suggest detailed knowledge regarding the way climate affect local populations are often necessary to predict climate impact successfully. TOPIC 3: Characterization of the individual success of a wild ungulate species: Results of evolutionary studies may be useful to identify optimal strategies for the management and conservation of wild populations. There is a consensus that fitness is an essential concept to understand the evolutionary processes in a natural context but a critical quantity to estimate. Therefore in this study we try to address two crucial questions: a) How many generations do we need to follow in the field to obtain a reliable estimate of fitness? and. b) Which of the fitness surrogates commonly used in the bibliography perform best? In this study we first show, via population model simulations that fitness, or expected individual genetic representation, asymptotes with time. This indicates that there is an optimum number of generations to be considered in fitness calculations. We also show that this optimum depends on the characteristics of the population we are measuring and its stochasticity context. Second, we present a new fitness surrogate which combine pt(1) defined by Coulson et al (2006) and ind proposed by McGraw & Caswell (1996). A priori, this index could be considered a reasonable improvement of these indexes but it was a poorer proxy at predicting future genetic representation. Third, we compare the known genetic representation in future generations with the estimated contribution quantified using seven different individual fitness surrogates to contrast their performance at predicting future genetic contribution. This comparison is achieved by using population simulations and the long-term dataset (>35 years) of individually marked red deer from the Isle of Rum. We find that pt(i) and LRS are equally the best fitness surrogates to estimate individual future genetic contribution. However, the performance of the other individual fitness surrogates at estimating an individual's expected future genetic representation within a population vary depending on the characteristics of the population we are measuring and its stochastic context.