Blind shots: non-natural mortality counteracts conservation efforts of a threatened waterbird

Waterbirds are particularly affected by the high hunting pressure they face in many regions, which in some cases is compromising conservation actions for threatened species. The marbled teal Marmaronetta angustirostris is one of the most endangered waterbirds in Europe. In order to restore its population, several conservation actions have recently been undertaken, including a population reinforcement programme in Spain using captive-bred birds. With the aim of assessing the success of the reinforcement programme to establish a long-term self-sustaining population, we identified mortality causes of marbled teal, evaluated the survival of individual birds of the reinforcement programme and estimated the viability of the population under different management scenarios. We used data from wild and captive-bred individuals tracked by GPS since 2018 (n = 42) and from a mark–recapture programme initiated in 2015 (n = 297). We recovered 15 dead birds or transmitters: 20% died of natural causes, 60% of non-natural causes (including all anthropic causes) and 20% of unknown causes. Furthermore, the GPS tags of 24 birds unexpectedly stopped transmitting without any indication of malfunction, and for 66.7% of these disappeared birds, the cessation was suspected to be caused by illegal shooting. Survival during the hunting season was higher for males (31.3%) than for females (12.5%), and for the wild (50%) than for the captive-bred birds (9.4%), probably due to differences in migration patterns to North Africa. Population viability models revealed that maintaining the breeding population at the current mortality rates is only possible with a permanent release programme of captive-bred individuals, and that in order to establish a self-sustaining population, non-natural mortality would have to be reduced by at least 40%. We recommend management measures to reduce marbled teal mortality, such as limiting legal hunting to hours with clear visibility, prosecuting illegal shootings, controlling exotic predators and improving water management to reduce disease outbreaks. Some improvements can be implemented in captive-breeding programmes, such as earlier release times and incorporating anti-predator training.The transmitters were funded by the Generalitat Valenciana, the Ministry for Ecological Transition and the Biodiversity Foundation. JMPG was supported by a Spanish Ministry of Science, Innovation and Universities postdoctoral contract IJC-2019-038968 funded by MCIN/AEI/10.13039/501100011033. ESG and ASA received the grants RYC2019-027216-I and RYC-2017-22796 funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in your future. RCRC was supported by the European Union-Next Generation EU in the Maria Zambrano Program (ZAMBRANO 21-26). The present research was carried out within the framework of the activities of the Spanish Government through the ‘Maria de Maeztu Centre of Excellence’ accreditation to IMEDEA (CSIC-UIB) (CEX2021-001198)

Body size variation in a lineage of spur-thighed tortoises (Testudo graeca whitei) contrasts with that expected from the species level

Ectotherms exhibit varying geographic size patterns shaped by environmental and evolutionary factors. This variability is noticeable within taxonomic groups. For instance, certain testudinids follow Bergmann’s rule (body size increases with latitude) and Rensch’s rule (sexual size dimorphism correlates with body size), while others do not. Here we hypothesize that body size patterns can even vary within a monophyletic lineage. To address this, we evaluated the body size patterns of the spur-thighed tortoise Testudo graeca that globally follows Bergmann’s and Rensch’s rules. We specifically investigated the influence of climate variables, latitude and elevation within the subspecies T. g. whitei throughout its natural distribution in North Africa, and in a recently expanded range in SE Spain (20 kya old). We found that males were smaller than females in both regions. The tortoises from SE Spain were smaller than those from North Africa, which showcased the smallest sizes ever reported for the species. Latitude was the main variable to explain tortoise body size. In particular, body size decreased with latitude in both regions, which contrasts with Bergmann’s rule expectations based on species-level findings. Finally, to further contradict species-level expectations, we did not find any statistical correlation between sexual size dimorphism and body size across the two studied regions. Such contradictory outcomes reveal complex geographic size patterns within T. graeca and raise conservation questions about demographic viability at smaller-sized sites.This work was supported by Projects PID2019-105682RA-I00 and TED2021-130381B-I00, funded by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033), the last also with the support of the European Union “NextGenerationEU”/PRTR”; and by funding from the Regional Valen cian Government (AICO/2021/145). The Miguel Hernández University provided support for several stays of MJS in the Ecology Area of the university. RCRC is supported by the European Union-Next Generation EU in the Maria Zambrano Programme (ZAMBRANO 21-26). The Dirección General de Gestión del Medio Natural of Andalusian Government (SGB/FOA/AFR), the Dirección General de Medio Natural of the Murcia Region and the Ministère de l’Agriculture, de la Pêche Maritime, du Développement Rural et des Eaux et Forêts Pêche Maritime, Département des Eaux et Forêts, decisión No. 19/2022 (DEF/DLCDPN/DPRN/CFF), authorized and facilitated sampling

Population density of the spur-thighed tortoise Testudo graeca declines after fire in north-western Africa

Fire is a key ecological process in several biomes worldwide. Over recent decades, human activities (e.g. rural abandonment, monoculture plantations) and global warming are magnifying the risk of fire, with changes in fire intensity and frequency. Here, we offer the first study that examines the impact of fire on the spur-thighed tortoise Testudo graeca living in a native cork oak forest and pine plantation in north-western Africa. A total of 44 transects (22 burnt and 22 unburnt) were sampled at 8 sites affected by fires of natural cork oak forest and pine plantation with 8 surveys per site in 2015–2017 (264 hours of sampling effort). Tortoise densities were estimated with line-transect distance sampling. The detection probability of tortoises was higher in burnt (0.915) than unburnt (0.474) transects. The density of tortoises was negatively associated with elevation and declined with fire by c. 50% in both forest types. The negative response of T. graeca to fire should be considered in conservation planning of this species in north-western Africa in a future scenario of changes in fire regime.BC, SF, and XS received a grant coded (2015-1) from Instituto de Estudios Ceutíes (https://www.ieceuties.org) to cover part of the fieldwork. The work of EG and RCRC was supported by the Spanish Ministry of Economy, Industry and Competitiveness and European Regional Development Fund (Project CGL2015- 64144; MINECO/FEDER)

Assessing DESS solution for the long-term preservation of nematodes from faecal samples

Preservation of biological samples is a relevant issue for many scientific disciplines. Although traditional preservers, such as formaldehyde or ethanol, imply major disadvantages related to health risks, DNA degradation and distortion of structures, they are widely used. Hence, the search for viable alternatives preserving morphometry and genetics seems necessary. Here we assess the suitability of DESS solution to preserve adult nematodes and their eggs in faeces. Concretely, faecal samples of terrestrial tortoises with oxyurids were used to: (i) compare the 1-month storage efficacy of eggs from different conservation protocols (faeces without preserver at -20 °C, faeces with DESS solution at room temperature, faeces with DESS solution at -20 °C and faeces with ethanol 70% at room temperature); (ii) address morphological nematode identification after 2 years of storage with DESS. We also corroborated that nematode DNA remained viable after 2 years. Overall, our results showed that DESS solution at room temperature is an advisable alternative to conserve both parasite eggs and adult nematodes for morphological identification and genetic purposes. It also offers the advantages of being low-cost, safe and suitable for fieldwork conditions and shipments without refrigeration for nematode preservation.MG was supported by a contract for postdoctoral researchers from the Generalitat Valenciana with reference APOSTD/2021/181. RCRC was supported by the European Union-Next Generation EU in the Maria Zambrano Program (ZAMBRANO 21-26). This research had the financial support of project PID2019-105682RA-I00, funded by the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033

Shorter telomeres are associated with shell anomalies in a long-lived tortoise

Age-related telomere length (TL) variation is relatively well-described for mammals, birds and other model organisms. Nevertheless, it remains largely unknown in ectotherms, especially turtles and tortoises, which are extremely long-lived species with slow or negligible senescence. In this study, we described TL dynamics in wild spur-thighed tortoises (Testudo graeca), one of the chelonian species with the lowest aging rates. By combining cross-sectional (single) and longitudinal (capture–recapture) samplings, we assessed the relationship between TL and individual characteristics (sex, age, individual growth rate, body condition index, presence of shell anomalies). We did not find any association between TL and sex, individual growth rate, or body condition. However, the relationship with age remains uncertain, likely due to the complex dynamics of TL over time. Interestingly, shorter telomeres correlated significantly with shell anomalies, which are usually assumed as a fitness proxy for reptiles. Overall, our results suggest TL as a potential indicator for ontogenetic studies on tortoises, while its utility as a marker of biological age appears limited.This work was supported by Project PID2019-105682RA-I00 and TED2021-130381B-I00, funded by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033), the last also with the support of the European Union ‘NextGenerationEU/PRTR’. RCRC is supported by the European Union-Next Generation EU in the Maria Zambrano Programme (ZAMBRANO 21-26)

Low tortoise abundances in pine forest plantations in forest-shrubland transition areas

The Spanish Ministry of Science and European Regional Development Fund funded this work through Projects CGL2012-33536 and CGL2015- 64144; MINECIO/FEDER. Regional Government of the Community of Valencia supported R.R-C. by a postgraduate grant (ACIF/2010/133) and E.G. by a postdoctoral grant (APOSTD/2015/048).In the transition between Mediterranean forest and the arid subtropical shrublands of the southeastern Iberian Peninsula, humans have transformed habitat since ancient times. Understanding the role of the original mosaic landscapes in wildlife species and the effects of the current changes as pine forest plantations, performed even outside the forest ecological boundaries, are important conservation issues. We studied variation in the density of the endangered spur-thighed tortoise (Testudo graeca) in three areas that include the four most common land types within the species’ range (pine forests, natural shrubs, dryland crop fields, and abandoned crop fields). Tortoise densities were estimated using a two-stage modeling approach with line transect distance sampling. Densities in dryland crop fields, abandoned crop fields and natural shrubs were higher (>6 individuals/ha) than in pine forests (1.25 individuals/ha). We also found large variation in density in the pine forests. Recent pine plantations showed higher densities than mature pine forests where shrub and herbaceous cover was taller and thicker. We hypothesize that mature pine forest might constrain tortoise activity by acting as partial barriers to movements. This issue is relevant for management purposes given that large areas in the tortoise’s range have recently been converted to pine plantations.Publisher PDFPeer reviewe

Sperm storage reduces the strength of the mate‐finding Allee effect

Mate searching is a key component of sexual reproduction that can have important implications for population viability, especially for the mate‐finding Allee effect. Interannual sperm storage by females may be an adaptation that potentially attenuates mate limitation, but the demographic consequences of this functional trait have not been studied. Our goal is to assess the effect of female sperm storage durability on the strength of the mate‐finding Allee effect and the viability of populations subject to low population density and habitat alteration. We used an individual‐based simulation model that incorporates realistic representations of the demographic and spatial processes of our model species, the spur‐thighed tortoise (Testudo graeca). This allowed for a detailed assessment of reproductive rates, population growth rates, and extinction probabilities. We also studied the relationship between the number of reproductive males and the reproductive rates for scenarios combining different levels of sperm storage durability, initial population density, and landscape alteration. Our results showed that simulated populations parameterized with the field‐observed demographic rates collapsed for short sperm storage durability, but were viable for a durability of one year or longer. In contrast, the simulated populations with a low initial density were only viable in human‐altered landscapes for sperm storage durability of 4 years. We find that sperm storage is an effective mechanism that can reduce the strength of the mate‐finding Allee effect and contribute to the persistence of low‐density populations. Our study highlights the key role of sperm storage in the dynamics of species with limited movement ability to facilitate reproduction in patchy landscapes or during population expansion. This study represents the first quantification of the effect of sperm storage durability on population dynamics in different landscapes and population scenarios.Financial support was granted by the Spanish Ministry of Economy, Industry and Competitiveness, and by the European Regional Development Fund (Projects CGL2012-33536, CGL2015-64144; MINECO/FEDER, UE). M.V.J.F. was supported by a “Juan de la Cierva-formación” postdoctoral grant of the Spanish Ministry of Economy and Competitiveness (reference JCI-2015-23508), a José Castillejo travel fund (reference CAS17/00225) from the Spanish Ministry of Education, Culture and Sport and a postdoctoral grant funded by the Regional Valencian Government and the European Social Fund (APOSTD/2018/043). A.S.A. was supported by a Vicenç Mut contract co-funded by the Regional Government of the Balearic Islands and the European Social Fund (PD/003/2016). A.S.A and J.D.A were supported by a Ramón y Cajal contracts (RYC-2017-22796 and RYC-2017-22783 respectively) co-funded by the Spanish Ministry of Science, Innovation and Universities, the State Research Agency and the European Social Fund. E.G. was supported by the Regional Valencian Government with a postdoctoral grant (APOSTD/2015/048)

Predation impact on threatened spur-thighed tortoises by golden eagles when main prey is scarce

A reduction in adult survival in long-living species may compromise population growth rates. The spur-thighed tortoise (Testudo graeca) is a long-lived reptile that is threatened by habitat loss and fragmentation. Golden eagles (Aquila chrysaetos), whose breeding habitats overlap that of tortoises, may predate them by dropping them onto rocks and breaking their carapaces. In SE Spain, the number of golden eagles has increased in the last decades and the abundance of their main prey (i.e., rabbits Oryctolagus cuniculus) has decreased. Our aims were to 1) describe the role of tortoises in golden eagles’ diet, and 2) estimate the predation impact of golden eagles on tortoises in eagles’ territories and in the regional tortoise population. We collected regurgitated pellets and prey remains under eagle nests and roosts, and obtained information on tortoise abundance and population structure and rabbit abundance. We found that tortoises were an alternative prey to rabbits, so that eagles shifted to the former where the latter were scarce. The average predation rate on tortoises was very low at the two studied scales. However, eagles showed a marked selection for adult female tortoises, which led the tortoise sex ratio to be biased towards males in those eagle territories with higher tortoise predation. Whether this may compromise the spur-thighed tortoise long-term population viability locally deserves further attention.Much information on the spur-thighed tortoise populations and the regional abundance model was obtained with Projects CGL2012-33536 and CGL2015-64144 funded by the Spanish Ministry of Science and the European Regional Development Fund, Grant PID2019-105682RA-I00, funded by MCIN/AEI/10.13039/501100011033 and AICO/2021/145 funded by the Regional Valencian Government. MM was supported by a Ramón y Cajal research contract from MINECO (RYC-2015-19231), MCM by a pre-doctoral grant of the Spanish Ministry of Science (FPU1700633), and RCRC by a postdoctoral grant funded by the Regional Valencian Government (APOSTD/2020/090) and by the European Union-Next Generation EU in the Maria Zambrano Program (ZAMBRANO 21-26). The Dirección General de Gestión del Medio Natural of Andalusian Government (SGB/FOA/AFR) and the Dirección General de Medio Natural of the Murcia Region authorised and facilitated the sampling of golden eagle territories (AUF20140061) and the spur-thighed tortoise populations (SGYB/AF/DBP, SGYB/AFR/DBP, AUF20160056, AUF20140057)

From individuals’ movement to range shifts: integration of movement data in individual-based models to assess global change effects on populations

El estudio del movimiento de los individuos informa directamente sobre los tamaños de las áreas de campeo, las rutas migratorias o la selección de hábitat. Pero, además, la integración de datos de movimiento en modelos ecológicos permite además abordar mayores escalas. En este trabajo mostramos los resultados de nuestra línea de investigación utilizando STEPLAND, un modelo basado en el individuo de desarrollo propio. El modelo se parametrizó con datos de movimiento, demográficos y genéticos de tortugas terrestres (Testudo graeca) del SE de España. Llevamos a cabo diferentes experimentos de simulación con el fin de contestar a cuestiones sobre los efectos del cambio global en la conservación de la especie. A nivel de especie, identificamos aquellos rasgos evolutivos de las tortugas, como el almacenamiento de esperma por parte de las hembras, que evitan las extinciones en hábitats antropizados. A escala de paisaje, evaluamos el impacto del abandono agrícola y la intensificación en la dinámica poblacional de esta especie de vida larga. La intensificación afectó negativamente las tasas reproductivas, la densidad de población y la probabilidad de extinción de T. graeca, con respuestas de retardo de 20, 30 y 130 años respectivamente. Finalmente, en un contexto regional, pretendemos simular las primeras etapas de una expansión. Los primeros resultados sugieren patrones característicos de surfing genético, un proceso que afecta la expansión de especies de baja dispersión afectadas por deriva genética. Creemos que nuestra línea de investigación ejemplifica bien que el valor científico de los datos de movimiento excede el nivel de individuo.The study of the movement of individuals directly informs about home-range sizes, migratory routes or habitat selection. But also, integrating movement into ecological models allows for larger-scale studies. Here we summarize the results of our line of research based in the individual-based model STEPLAND. The model was parameterized with movement, demographic and genetic data of spur-thighed tortoises (Testudo graeca) in SE Spain. We developed different simulation experiments to answer questions about the effects of global change on the conservation of this species. At the species level, we identified those evolutionary traits of tortoises, such as female sperm storage, that prevent extinctions in human-altered habitats. At landscape scale, we assessed the impact of agricultural abandonment and agricultural intensification on the population dynamics of this long-lived species. Only agricultural intensification negatively affected reproductive rates, population density, and probability of extinction of T. graeca, with time-lag responses of 20, 30 and 130 years respectively. Finally, in a regional context, we aim to simulate the early stages of a range expansion. Preliminary results reveal patterns compatible to “genetic surfing”, a process affecting the expansion of low dispersal species impacted by strong genetic drift. We believe that our line of research exemplifies well that the scientific value of movement data goes well beyond the individual level.Esta línea de investigación se ha sufragado con las ayudas PID2019-105682RA-I00, financiada por MCIN/AEI/10.13039/501100011033; y por CGL2015-64144, con financiación de MINECO/FEDER (UE). El contrato de R.C.R.C. se sufraga con una ayuda del programa María Zambrano (ZAMBRANO 21-26), con fondos European Union-Next Generation (EU). A.S.A. y J.D.A. cuentan con ayudas Ramón y Cajal del Ministerio de Ciencia (RYC-2017-22796 y RYC-2017-22783, respectivamente). M.V.J.F. tiene un contrato Juan de la Cierva Incorporación (IJC2019-039145-I) de este mismo organismo y ella y A.S.A. cuentan con financiación a Grupos Emergentes (CIGE/2021/157) de GVA