New publication : vultures as sentinels!

Curk, T. Santangeli, A., [...] Melzheimer, J. 2025 Using animal tracking for early detection of mass poisoning events. Journal of Applied Ecology. DOI: 10.1111/1365-2664.70128

 In a shell: Tracking just a small portion of the vulture population can significantly reduce poisoning-related deaths. This study shows that GPS-tracked vultures can serve as effective sentinels, enabling quicker poisoning detection and response, offering a cost-effective and practical strategy to inform conservation efforts.

 Abstract: 

 1. Amidst the sixth mass extinction, some animal groups, such as vultures, the only obligate scavengers among vertebrates, are disappearing at an unprecedented rate. Vulture populations worldwide are declining, primarily due to poisoning. As many vulture species are social foragers, they can congregate in large numbers to scavenge at a carcass, potentially increasing their exposure to poisoning risk. Current anti-poisoning prevention and mitigation measures are insufficient to tackle this threat. There is an urgent need for new effective strategies to prevent mass vulture mortality. 

2. In this study, we applied agent-based modelling using white-backed vulture (Gyps africanus) data from Namibia to: (1) quantify the impact of different foraging strat-egies on vulture poisoning risk and (2) evaluate the cost-effectiveness of using vultures as sentinels for poisoning detection. This approach involves GPS tracking of various numbers of vultures and using the data to quickly detect poisoning in-
cidents and decontaminate carcasses. These actions help mitigate further vulture mortality and prevent mass poisoning. 

 3. Our findings demonstrate that social foraging significantly increases the risk of poisoning among white-backed vultures. However, GPS tracking of individual vultures enables earlier detection of poisoning events, thereby reducing associated mortalities. Poisoning mitigation effectiveness improves with both the number of tracked individuals and the speed of decontamination response. According to
our agent-based model tailored to our study system and species, tracking approximately 5% of the population (25 individuals) offers a good balance between cost and effectiveness, requiring an estimated budget of USD 60,000. Using this strategy and approach, and assuming a response time within 2 h, up to 45% of poisoning-related deaths could be prevented.

4. Synthesis and applications: Our results suggest that, in order to reduce mortality incidences from poisoning in our study system and species, it is sufficient to track a small proportion of the vulture population, which would act as sentinels for the rest. By evaluating the costs and ecological benefits of alternative strategies, varying in number of birds tagged or response time, we provide evidence-based solutions that practitioners can use to design conservation plans. These findings are therefore instrumental in supporting vulture and scavenger conservation policy and practice.

Exhibition at the Natural History Museum in Soller: the video

 Here is a short video by A. Rotger of the exhibition at the Natural History Museum in Soller "When data speak". The exhibition will last until the next spring. Don't miss it!!

 

 

Exhibition at the Natural History Museum in Soller !

Friday 23rd of May there will be the opening of the exhibition "WHEN DATA SPEAKS: THE HEARTBEAT OF BALEARIC WILDLIFE" at the Botanical Garden of Sóller / Museum of Natural Sciences - MUCBO next Friday, May 23rd at 7:00 PM.

The exhibition will present the results of the project BIO2022/003 "Impact of multiple threats on population trends of terrestrial vertebrate species in the Balearic Islands." carried out by Dr. A. Rotger and Dr. A Ana Sanz-Aguilar from the GEDA.

It aims to raise awareness about Balearic terrestrial vertebrate fauna, the threats they face, and the importance of scientific monitoring to improve their conservation.

New Thesis defense with the GEDA!

Guillermo Gómez López had just obtained his Ph.D. at the University Complutense of Madrid with a thesis titled "Unravelling offspring sex ratios and survival in Old World vultures: insights from long-term monitoring" supervised by A. Sanz-Aguilar, G. Blanco y M. Carrete.  The thesis obtained the maximum note with laude. Congratulations Guillermo!!! Well done!!

New publication on immigrationa and population turnover!

Natsukawa, H., Tavecchia, G., Frías, Ó., Sergio, F., Hiraldo, F., Blanco, G. 2025 Immigration hides the decline caused by an anthropogenic trap and drives the spectacular increase of a mobile predator. Oecologia 207, 15 (2025). https://doi.org/10.1007/s00442-024-05656-2

In a shell:This study shows how massive immigration into a contaminated population of black kites, driven by an increased food supply and flock attraction, transformed a declining trend into a population increase, while highlighting the potential risks of anthropogenic subsidies as evolutionary traps

Abstract:  Accurate identification of decreasing trends is a prerequisite for successful conservation, but can be challenging when immigration compensates local declines in abundance. Here, we show that a potential declining trend driven by low vital rates was overridden and converted into a spectacular increase by massive immigration into the population of a semi-social raptor, the black kite Milvus migrans, breeding in a highly contaminated area near a major landfill. Immigration was promoted by a growing food-base of live prey, coupled with the attraction exerted by the progressive gathering of a large flock of non-breeders at the area, resulting in an “attraction spiral” that lured large numbers of breeders to settle into a contaminated population incapable of self-sustenance. Immigration was so prevalent that, in little more than a decade, over 95% of the original population was substituted by immigrants, which showed the enormous potential of immigration as a rescue mechanism. At the same time, immigration may hide cryptic threats, as shown here, and expose some species, especially group-living mobile ones, to rapid attraction to anthropogenic subsidies, whose potential role as evolutionary traps is well known. The dynamics exposed here may become increasingly common, affecting many other species in our growingly anthropogenic world. Our results remark the often overlooked importance of immigration in ecology, evolution, and conservation as a key player for population dynamics and their more realistic forecast.

 

 

New publication: IPM and tortoise populations!

Segura A., Rotger, A. and Rodriguez-Caro, R., 2025. Hidden Threats to Persistence: Changes in Population Structure Can Affect Well-Preserved Spur-Thighed Tortoise Populations. Herpetologica. https://doi.org/10.1655/Herpetologica-D-23-00066

In a shell: This study on Spur-thighed Tortoises highlights a shift towards a female-biased population, with high juvenile mortality from raven predation, and emphasizes the importance of female survival and sex-ratio especially in the context of climate change.

Abstract:  Population structure and survival are key components of wildlife management. Long-term monitoring of long-lived species, particularly those with indeterminate growth, is crucial when studying demographic processes. Here, we examined a population of Spur-thighed Tortoises, Testudo graeca, over a 7-yr period (17% of its life span), including changes in population structure, causes of mortality, and growth patterns. We found a change in population structure, as evidenced by lower young adult density (both males and females) and a more female-biased population compared to the start of the study. Juvenile mortality was high, and the main cause was predation by common ravens. 

Photo from iNaturalist

For adults, mortality was relatively low and was mostly observed in winter or due to anthropogenic reasons (forestry or road mortality). We also modeled adult size-dependent survival and juvenile threshold survival (minimum number of juveniles needed to reach the adult stage to maintain population viability) using a Bayesian framework and matrix projection models, respectively. Adult survival was high (0.97), but with variation between the sexes. Female survival was not size dependent, but male survival decreased when size exceeded 150 mm carapace length. In this population, longer female life spans and climate change effects seemed to be the most likely reasons for our female-biased population. This study particularly pinpoints the importance of high survival in older females, which contributes to species credit, and stresses the negative potential of low juvenile and male densities in the population. Indeed, the annual juvenile threshold survival range was estimated between 0.32 and 0.49, not accounting for the predation exerted by common ravens in subadults. Therefore, if predation reduces juvenile survival rates below this threshold, population viability can be affected in the future. The study contributes to this species’ conservation by anticipating time-lagged demographic responses based on current climate trends (less annual rainfall and more days over 40°C) and predation.

GEDA at 11F

GEDA joined the activities of the International Women and Girls on Science.

Dr. A. Sanz-Aguilar explained her research and spoke about her experience to children at school. 

 

Upcoming activities at IMEDEA can be found here

GEDA at the 26th Spanish Ornithological Congress! (I)

GEDA is participating to the Spanish Ornithological Congress held in Valencia (12-16 of February program here). The contributions, from seabirds to ticks to demographic trends of Balearic vertebrates, illustrate the work of GEDA members.