Using retrospective life tables to assess the effect of extreme climatic conditions on ungulate demography.

In Mediterranean areas, severe drought events are expected to intensify in forthcoming years as a consequence of climate change. These events may increase physiological and reproductive stress of wild populations producing demographic changes and distribution shifts. We used retrospective life tables to understand demographic changes on a wild population after severe drought events. We studied the impact of two extreme events (2003 and 2005) on the population dynamics of our model species, the red deer (Cervus elaphus). During both years, population density was high (40 and 36 ind/100 ha, respectively). Thus, we reconstructed retrospectively the age structure of the female part of the population for the period 2000-2010 by using data of known-age individuals culled during the period 2000-2019 (n = 4176). Also, based on previous study results, we aimed to validate this methodology. Both extremely dry years, 2003 and 2005, produced marked and lasting cohort effects on population demography. Age pyramid the following years (2004 and 2006) revealed that the extreme drought caused the female fawn cohort to be similar or even smaller than the yearling cohort. Furthermore, these cohort effects were still perceptible 3 years after these severe events. Results agree with previous findings that showed a negative effect of severe drought events on female pregnancy rates and conception dates. Although simple, this study provides an empirical quantification of the demographic effects of severe drought events for a wild population which might be useful to understand future demographic changes under the context of climate change.

Assessing red deer hunting management in the Iberian Peninsula: the importance of longitudinal studies.

Understanding the dynamics of a wildlife population in relation to hunting strategies is essential to achieve sustainable management. We used monitoring data over 25 years from two red deer (Cervus elaphus) populations with different management (with and without supplemental feeding) in South Central Spain to: (i) characterise the density dependence of population dynamics under contrasted management, and (ii) provide the basis for sustainable extraction by considering the theoretical maximum sustainable yield (MSYt) as the reference. The red deer population displayed a typical management reactive culling approach ('saw-tooth-like' curves), with occasional strong annual harvests but not occurring on a regular basis. Interestingly, we found reduced population growth at high densities in both populations, indicating that density-mediated factors determined population growth even when artificial feeding was provided. However, no effects of sex not age class of the extracted population on the population growth rate were determined. The total number of animals hunted was only slightly above those predicted by MSYt (i.e. K 50%) in both populations, despite high densities close to theoretical K, being consistent throughout the study period. The extraction rates (30.3 and 34.0%, for supplemented and unsupplemented populations, respectively) were 13.3% and 10.2% lower compared to the MSYt situation in the unsupplemented and supplemented populations, respectively. Long term population monitoring data provided feasible and suitable baseline values to optimise the sustainable exploitation of red deer populations in the Mediterranean ecosystem under these contrasting management scenarios. Adaptive management, involving objective-driven decision making informed by data on red deer population dynamic, can contribute (i) to maximising the total extraction over the long term while (ii) reducing the ecological impact of high population densities.

Climate, female traits and population features as drivers of breeding timing in Mediterranean red deer populations.

Understanding the factors that lead to variation in the timing of breeding in widespread species such as red deer (Cervus elaphus) is crucial to predict possible responses of wild populations to different climate scenarios. Here, we sought to further understand the causes of inter-annual variation in the reproduction timing of female deer in Mediterranean environments. An integrative approach was used to identify the relative importance of individual, population and climate traits in the date of conception of free-ranging deer, based on a dataset of 829 hinds culled during 12 years. We found that a population trait, density, was the most important factor explaining the variation in conception dates, with greater densities causing later conception dates. Body mass was the second in importance, with heavier females conceiving earlier than lighter ones. Almost equally important was the spring real bioclimatic index, a measure of plant productivity, causing later conception dates in the least productive springs (drier and hotter). Another climatic component, the end of summer drought, showed that the sooner the autumn arrives (greater rainfalls and cooler temperatures) the earlier the conception dates. Interestingly, age class was found to be a minor factor in determining conception date. Only older females (≥10 years old) conceived significantly later, suggesting reproductive senescence. This study highlights not only the importance of population and individual traits but also the influence of climatic parameters on the deer reproductive cycle in Mediterranean environments, giving valuable insight into how reproductive phenology may respond to seasonality and global climate changes.

Different hunting strategies select for different weights in 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 (Cervus elaphus) 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.

Nodular onchocercosis of red deer in central Spain.

The presence of nodular onchocercosis was investigated post-mortem in 142 red deer (11 calves, 35 yearlings and 96 adults) shot from February 1998 to January 1999, and July-November 1999 in "Quintos de Mora" (Toledo, central Spain), a game property belonging to the National Wildlife Reserves. Between 6 and 13 animals were analysed monthly by inspection for subcutaneous nodules of Onchocerca spp. Subcutaneous nodules of Onchocerca sp. were detected in 24% of the animals. Anatomical locations for nodules were the back and flanks. Infection ranged from 1 to 29 nodules per animal. Adult worms collected from nodules were identified as O. flexuosa. No apparent seasonal trend was observed either in prevalence or in mean intensity of infection, which fluctuated between 48% (5+/-8 nodules) in winter 1998 and 5% (1+/-0 nodules) in summer 1999. Prevalence of infection was significantly higher in adult (30%) than in young animals (9% in calves, 11% in yearlings), although no age effect on intensity was observed. The size of the nodules was measured to evaluate the age of infection. Small (recent) nodules (5-6mm of diameter) were collected in late spring, summer and fall; medium-sized nodules (12-15 mm) were in second half of summer, fall and winter, and large (mature) nodules (20-25 mm) in fall, winter and part of spring. Significant differences were found among host age groups.