New Publication on Lizard lifspan!

Rotger, A., Tenan, S., Igual, J.-M, Bonner, S. and Tavecchia, G., 2022. Life span, growth, senescence and island syndrome: Accounting for imperfect detection and continuous growth Journal or Animal Ecology,https://doi.org/10.1111/1365-2656.13842

Abstract:

1. Small vertebrates on islands are expected to attain a larger body size, and a greater survival than their mainland counterparts. Comparative studies have questioned whether lizards exhibit this set of adaptations, referred to as the ‘island syndrome’.
2. We collected data on 730 individuals the endemic Lilford's lizard Podarcis lilfordi throughout a 10-year period on a small island of the Balearic archipelago (Spain). We coupled a growth function with a capture–mark–recapture model to simultaneously estimate size- and sex-dependent growth rate and survival. To put our results into a wider context, we conducted a systematic review of growth, life span and age at maturity in different Podarcis species comparing insular and mainland populations.
   
   
   
3. We found a low average growth coefficient (0.56 and 0.41 year⁻¹ for males and females to reach an asymptotic size of 72.3 and 65.6 mm respectively), a high annual survival probability of 0.81 and 0.79 in males and females, and a large variability between individuals in growth parameters.
4. Survival probability decreased with body size in both sexes, indicating a senescence pattern typical of long-lived species or in populations with a low extrinsic mortality. Assuming a constant survival after sexual maturity, at about 2 years old, the average life span was 6.18 years in males and 8.99 in females. The oldest animal was a male last captured at an estimated age of ≥13 years and still alive at the end of the study.
5. Our results agree with the predictions of the ‘island syndrome’ for survival, life span and growth parameters. A comparative analysis of these values across 29 populations of 16 different species of Podarcis indicated that insular lizards grow slower and live longer than their mainland counterparts. However, our data differed from other island populations of the same species, suggesting that island-specific characteristics play an additional role to isolation.
6. Within this study we developed an analytical approach to study the body size-dependent survival of small reptiles. We discuss its applicability to contrast hypotheses on senescence in different sexes of this species, and provide the code used to integrate the growth and capture–mark–recapture models.

New publicatoion: when and where Black Kites die !

Sergio, F., Tavecchia, G., Tanferna, A., Blas, J., Blanco, G., and Hiraldo, F. 2019: When and where mortality occurs throughout the annual cycle changes with age in a migratory birds: indiviudal vs population implications. Scientific Reports, 9, 17352.

Photo: F. Sergio

Abstract: The annual cycle of most animals is structured into discrete stages, such as breeding, migration and dispersal. While there is growing appreciation of the importance of different stages of an organism’s annual cycle for its fitness and population dynamics, almost nothing is known about if and how such seasonal effects can change through a species lifespan. Here, we take advantage of the opportunity offered by a long-term satellite/GPS-tracking study and a reliable method of remote death-detection to show that certain stages of both the annual and life cycle of a migratory long-lived raptor, the Black kite Milvus migrans, may represent sensitive bottlenecks for survival. In particular, migratory journeys caused bursts of concentrated-mortality throughout life, but the relative importance of stage-specific survival changed with age. On the other hand, the balance between short-stages of high mortality and long-stages of low mortality made population-growth similarly dependent on all portions of the annual cycle. Our results illustrate how the population dynamics of migratory organisms can be inextricably linked to ecological pressures balanced over multiple stages of the annual cycle and thus multiple areas of the globe, suggesting the frequent need for challenging conservation strategies targeting all portions of a species year-round range.

New Publication on Invasive species and uncertainty models ! (and Cover)

Senar, J.C., Arroyo, L., Ortega-Segalerva, A., Carrillo, J.G., Tomas, X., Montalvo, T., Sanz-Aguilar, A., 2019 Estimating age‐dependent survival when juveniles resemble females: Invasive ring‐necked parakeets as an example Ecology and Evolution https://doi.org/10.1002/ece3.4366

Photo M Cabrera

Abstract: Many species only show sexual dimorphism at the age of maturity, such that juveniles typically resemble females. Under these circumstances, estimating accurate age‐specific demographic parameters is challenging. Here, we propose a multievent model parameterization able to estimate age‐dependent survival using capture–recapture data with uncertainty in age and sex assignment of individuals. We illustrate this modeling approach with capture–recaptuPsittacula krameri. We analyzed capture, recapture, and resighting data (439 recaptures/resightings) of 156 ring‐necked parakeets tagged with neck collars in Barcelona city from 2003 to 2016 to estimate the juvenile and adult survival rate. Our models successfully estimated the survival probabilities of the different age classes considered. Survival probability was similar between adults (0.83, 95% CI = 0.77–0.87) and juveniles during their second (0.79, 95% CI = 0.58–0.87) and third winter (0.83, 95% CI = 0.65–0.88). The youngest juveniles (1st winter) showed a slightly lower survival (0.57, 95% CI = 0.37–0.79). Among adults, females showed a slightly higher survival than males (0.87, 95% CI = 0.78–0.93; and 0.80, 95% CI = 0.73–0.86, respectively). These high survival figures predict high population persistence in this species and urge management policies. The analysis also stresses the usefulness of multievent models to estimate juvenile survival when age cannot be fully ascertained.

New Publication on Woodcock mortality and hunting pressure

Prieto, N., Tavecchia, G., Telletxea, I, Ibañez, R., Ansorregi, F., Galdos, A., Urruzola, A., Iriarte, I. and Ariziaga, J. 2019 Survival probabilities of wintering Eurasian Woodcocks Scolopax rusticola in northern Spain reveal a direct link with hunting regimes. J. Ornithol. doi: 10.1007/s10336-018-1617-1

From en.wikipedia.org

Abstract  The management of game species relies on robust estimates of hunting-related mortality. A relative measure of this mortality can be obtained by comparing survival estimates of animals across similar areas with different hunting pressures. We conducted live recapture-dead recovery analyses on wintering Eurasian Woodcocks Scolopax rusticola (hereinafter “Woodcock”) in provinces of Gipuzkoa (GIP) and Álava (ALA), two neighboring regions of northern Spain. The two regions have a similar number of hunting licences issued on a per day basis, but while hunting is limited to 3days per week in ALA, in GIP it is allowed on a daily basis, resulting in a ca. 50% longer period of  exposure of game species to hunting-related mortality here.We used a model based on monthly survival estimates to test whether the mortality of Woodcock varied between the two regions. Mean (± SE from a time-constant model) annual survival of Woodcocks was estimated to be 0.37 (± 0.04) and 0.56 (± 0.04) in GIP and ALA, respectively. If we assumed that this difference was only due to the longer period of exposure to hunting, mortality was increased by ca. 10% per additional day of hunting per week. Moreover, we also found that survival was positively associated with temperature in one of the study zones (ALA), suggesting that a high hunting pressure can override the effect of climate-dependent fluctuations. However, further research into fecundity and dispersal is necessary to assess the viability and sustainability of the wintering Woodcock populations under the current hunting regimes in these two zones.

 

New Publication on modelling transient probability!

Sanz-Aguilar, A., Pradel, R. and Tavecchia, G. 2018 Age-dependent capture-recapture models and unequal time intervals. Animal Biodiversity and Conservation 42 (1), pag. 91-98  https://doi.org/10.32800/abc.2019.42.0091

Photo: M. Gomila

Abstract:Estimates of survival probabilities in natural populations can be obtained through capture–mark–recapture (CMR) models. However, when capture sessions are unevenly spaced, age–dependent models can lead to erroneous estimates of survival when individuals change age class during the time interval between two capture occasions.
We propose a solution to correct for the mismatch between time intervals and age class duration in two age class models. The solution can be implemented in different ways. The first consists of adding dummy occasions to the encounter histories and fixing the corresponding recapture probabilities at zero. The second makes use of the log–link function available in some CMR software (e.g. program MARK). We used simulated and real data to show that the proposed solution delivers unbiased estimates of age–dependent survival probabilities.

The VIII edition of the Workshop on CMRR analysis ended!

The VIII edition of the annual workshop on CAPTURE-MARK-RECAPTURE and RECOVERY analysis has ended last friday! Thanks for coming (although we have missed the very big shrimp :-) ! It has been great to have you all here at the IMEDEA and learn about dragon-flies, storks, cranes, swans, houbara bustard, audouin's gulls, penguins norway lobsters, black-tailed godwits, marking methods..etc.. and top of all, new exiting biological questions.  More next year!

 

GEDA at the I National Symposium on Raptors and their habitats

GEDA has participated to the I National Symposim on Raptors and their Habitats in Guara last week.

 Ana Sanz-Aguilar, Ainara Cortés-Avizanda and Jaume Badia-Boher have contributed with their work to the Symposium.