Frank Thomas Ussner Dellinger

@uma.pt

associate professor faculty of life sciences
University of Madeira

Frank Thomas Ussner Dellinger


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Thomas Dellinger is an Associate Professor of Biology at the University of Madeira (Portugal), working at the Funchal Marine Biology Station. His research focuses on behavioural ecology, marine biology and conservation, particularly the ecology of oceanic juvenile loggerhead sea turtles (Caretta caretta) in the North Atlantic. He also studies island reptiles, including the endemic Madeiran wall lizard (Teira dugesii). His work integrates field ecology, bycatch, telemetry and trophic ecology to understand marine megafauna and insular ecosystems in the Macaronesian region.

EDUCATION

Diplom-Biologe (MSc equivalent) in Biology, University of Konstanz, Germany (1987) with a thesis on the food niche of Galápagos furs seals and sea lions.
Dr. rer. nat. (PhD) in Biology, Ludwig-Maximilians-Universität München, Germany (1991), with research on the energetics of reproduction and population dynamics of marine iguanas in the Galápagos through the then Max-Panck Institute of Behavioral Physiology. The doctoral degree was later recognized as equivalent to a PhD by the University of Madeira (1995).

RESEARCH, TEACHING, or OTHER INTERESTS

Ecology, Evolution, Behavior and Systematics, Ecology

FUTURE PROJECTS

Oceanic search behaviour of loggerhead sea turtles in the North Atlantic

Subtropical ocean gyres are extremely oligotrophic environments with scarce and unpredictable food resources. This project uses oceanic juvenile loggerhead turtles (Caretta caretta) as a model to investigate how large vertebrates locate and exploit sparse prey in the open ocean. By combining satellite telemetry with in-situ observations using remotely operated vehicles (ROVs), the study links movement patterns with directly observed behaviour in the water column. The project tests whether movement states inferred from telemetry correspond to distinct behavioural modes related to prey detection and foraging. Results will improve understanding of search strategies in low-productivity marine environments and contribute to broader theories of movement ecology and marine megafauna conservation.


Applications Invited
Research partners and collaborators with complementary expertise for joint aplications

Development of a Sea Turtle Rehabilitation and Research Centre in Madeira

We are developing a sea turtle rehabilitation and research facility in Madeira (NE Atlantic, Macaronesia) to support the rescue, treatment, and study of stranded or injured marine turtles. The centre will integrate veterinary care, rehabilitation tanks, behavioural monitoring, and scientific research on turtle health, ecology, and conservation. In addition to rehabilitation, the facility will provide infrastructure for research on oceanic juvenile loggerhead turtles (Caretta caretta), including telemetry, behaviour, and bycatch mitigation studies. We seek collaborative projects that help equip and expand the facility while contributing to marine conservation research in the Macaronesian region.


Applications Invited
We are looking for research collaborators, institutions, NGOs for joint aplications
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Scopus Publications

Scopus Publications

  • Juveniles and where to find them: a basin-scale habitat model for the lost years of loggerhead sea turtles in the North Atlantic
    M. Bartolini, E. L. Hazen, H. Parra, K. A. Bjorndal, A. B. Bolten, et al.
    Movement Ecology, 2026
    Background Juvenile loggerhead sea turtles represent a crucial but understudied stage of the species life cycle. Most studies have been conducted at regional scales and there remains a need for a broader scale synthesis. In the North Atlantic, loggerheads encounter numerous threats such as fishing during their transoceanic journey, so it is important to get a broad view of their distribution, movement and habitat preferences. Methods For this study, we gathered tracking data from 124 juvenile loggerheads tagged along the Azores, Canary Islands, Madeira and in the western North Atlantic to develop a habitat model for the entire basin. We used a SSM to interpolate tracks to daily positions, simulated pseudo-absences with a correlated random walk for background data, and explored 17 environmental variables using boosted regression trees to select the best model in terms of biological realism and predictive power. The best model obtained (AUC = 0.988) was then used to predict habitat suitability for the North Atlantic for the period 1998–2022. Stranding records of loggerheads in France, UK and Ireland were used to discuss the predictions. Results After filtering, tracks of 105 individuals, covering most of the basin, were used in the model. Our predictions of habitat suitability show the importance of the Gulf Stream and the Azorean Current. Habitat suitability is predicted to be higher in the area between 30° and 45°N all year round, while open waters below 30°N, including Cape Verde, are not predicted to be a suitable habitat. In northern and eastern areas, like the Bay of Biscay and UK and Irish waters, habitat suitability varied seasonally, with colder seasons showing lower values. Accordingly, strandings in those areas occurred mostly during winter (December-February; 45.1%) and spring (March-May; 34.1%). Conclusions The model offers a first basin-scale prediction of the seasonal distribution of juvenile loggerheads in the North-Atlantic, which shows consistency with stranding and bycatch data in the basin. This study represents a first step towards a broader scale understanding of juveniles’ habitat preferences that can be used to quantify the magnitude and extent of the threats that they face.
  • Unraveling Spatio-temporal genetic connectivity of loggerhead sea turtles across the North Atlantic
    Françoise D. Lima, Catalina Monzón-Argüello, Hugo Parra, Marco Santos, Andrea Herguedas, et al.
    Basic and Applied Ecology, 2026
  • Global tracking of marine megafauna space use reveals how to achieve conservation targets
    Ana M. M. Sequeira, Jorge P. Rodríguez, Sarah A. Marley, Hannah J. Calich, Mirjam van der Mheen, et al.
    Science, 2025
    The recent Kunming-Montreal Global Biodiversity Framework (GBF) sets ambitious goals but no clear pathway for how zero loss of important biodiversity areas and halting human-induced extinction of threatened species will be achieved. We assembled a multi-taxa tracking dataset (11 million geopositions from 15,845 tracked individuals across 121 species) to provide a global assessment of space use of highly mobile marine megafauna, showing that 63% of the area that they cover is used 80% of the time as important migratory corridors or residence areas. The GBF 30% threshold (Target 3) will be insufficient for marine megafauna’s effective conservation, leaving important areas exposed to major anthropogenic threats. Coupling area protection with mitigation strategies (e.g., fishing regulation, wildlife-traffic separation) will be essential to reach international goals and conserve biodiversity.
  • TRITON—Open Telemetry and Location Estimation for Marine Monitoring Based on IoT and LoRa
    Marko Radeta, João Pestana, Pedro Abreu, Rúben Freitas, Francisco Silva, et al.
    IEEE Journal of Oceanic Engineering, 2025
  • Drivers of continuous colour variation in the Madeiran wall lizard (Teira dugesii)
    Prem Aguilar, Pedro Andrade, Thomas Dellinger, Miguel Ángel Carretero, Guillem Pérez i de Lanuza
    Biological Journal of the Linnean Society, 2024
    Animal coloration is often shaped by a myriad of factors that lead to differences in colour through changes in the chromatophores. Depending on how this variation is partitioned, coloration is often categorized as continuous or polymorphic. However, the boundaries between these two categories are not always clear. Here, we investigated whether the ventral coloration of the Madeiran wall lizard (Teira dugesii) varies continuously or corresponds to discrete colour morphs, via by-eye colour classification and visual modelling. By combining these two approaches, we show that T. dugesii coloration varies continuously and that colour classifications based on anthropomorphic approaches alone are ill suited to describe animal coloration. We also tested the influence of size, body condition, and sex as possible factors that might explain differences in T. dugesii coloration. We found that body condition, and especially size and sex, explain a great proportion of the variability observed in this species. These differences point to an effect of ontogeny, which might play a major role in colour development owing to the longevity of this species. Moreover, the sexual dichromatism that this species shows is indicative of an effect of sexual selection on coloration, perhaps explained by differences in circulating hormones.
  • New records of Oecanthus species (Orthoptera, Oecanthidae) in the Madeira archipelago
    Hugo Miguel Silva, Laura Avivar-Lozano, Gonçalo Gomes, Howon Rhee, Thomas Dellinger, et al.
    Journal of Orthoptera Research, 2024
    The Madeira and Porto Santo Islands have both witnessed substantial habitat loss since their initial colonization. Despite their small size and the degradation of their natural habitats, they harbor a rich diversity of terrestrial invertebrates, including a significant number of endemic species. While research on Orthoptera fauna has predominantly focused on the largest island of Madeira, the smaller island of Porto Santo has remained relatively understudied. Fieldwork on both islands has led to the discovery of Oecanthus dulcisonans Gorochov, 1993 in the Madeira archipelago (Porto Santo and Madeira) for the first time. This species was described based on specimens collected in Tenerife and the Arabian Peninsula. However, its distribution, which includes parts of Africa, Western Asia, and some localities in Southern Europe, remains poorly understood. Oecanthus dulcisonans is morphologically very similar to Oecanthus pellucens (Scopoli, 1763), the only species of this genus previously recorded for the island of Madeira. Due to this resemblance, doubts have arisen regarding which of these two species is present in Madeira. By examining new material of O. pellucens, we have confirmed the presence of this species on Madeira as well. These new findings highlight the fact that, for these species, the Madeira archipelago represents the western limit of their distributional ranges in the Palearctic region.
  • Strong negative effects of recent wildfires on two endemic Macaronesian bush-crickets
    Howon Rhee, Katharina Hauth, Kira Greis, Ortwin Elle, Thomas Dellinger, et al.
    Insect Conservation and Diversity, 2023
    Wildfires increase globally in frequency and extent as a consequence of climate change. These wildfires may have negative effects on insect populations. Macaronesia is a global biodiversity hotspot with wildfires occurring annually, but the consequences of these wildfires on endemic insects are poorly understood. Using bioacoustics monitoring, we studied the consequences of recent wildfires on two endemic silvicolous Macaronesian Bush‐Cricket species, which are listed as threatened on the IUCN Red List of Threatened Species. Our results show that wildfires had strong negative effects on populations of both species. However, when analysing the effects of fire history and size, we found that one of the species was found on older burnt sites, suggesting a capacity to recolonise smaller burnt areas from adjacent non‐burnt areas. Reducing wildfire frequency and size will be crucial to conserving the two species. Additionally, restoring native laurel forest vegetation will support the recovery of both species.
  • Dietary Variation Is Driven by Landscape Heterogeneity in an Insular Omnivorous Endemic Lizard, Revealed by DNA Metabarcoding
    Catarina Rato, Thomas Dellinger, Miguel A. Carretero
    Diversity, 2022
    Living on islands entails numerous challenges for animals, among which population density approaching the carrying capacity of trophic resources stands out. To overcome this limitation, many insular lizards can supplement their insectivorous diet with increasing portions of plant material. The Madeira wall lizard, Teira dugesii, is a medium-sized lacertid, endemic to the Madeira and Selvagens archipelagos. As common in this family, adults are sexually dimorphic with males being bigger than females. Previous dietary studies on morphological scatology identified a higher proportion of plant over animal prey items, changing according to the location and sex. Here, we used DNA metabarcoding to examine the diet of this lizard species quantifying it at a higher taxonomical resolution and enhancing the detection of soft-body prey that often go undetected in morphology-based studies. In a sample of 151 faecal samples from eight populations including different habitats and altitudes in Madeira, we identified 289 prey items belonging to eight animal and three plant Classes, encompassing 58 distinct orders and 140 families. Of these, 63 were identified up to the species level. The results support a strong trend towards herbivory in this species with plants representing almost 74% of the diet occurrences in contrast to the 26% of animal prey. Remarkably, the plant fraction of the diet remained stable across localities but varied with size and mass in males. As males grew bigger and heavier, they significantly increased their plant matter intake. Likely, larger bodies and abdomens allowed allocating longer and more complex digestive tracts harbouring intestinal flora to better decompose plant organic compounds. This allowed heavier animals to have a richer diet regime. However, diet richness and composition were not affected by either sex or size, while the locality had a significant effect on both diet components likely in response to local variation in prey availability. By including an increasing plant fraction into a primarily insectivorous diet, this insular lizard has not only enlarged its trophic niche but is also able to exploit more efficiently the highly variable resources provided by insular environments.
  • Drivers of litter ingestion by sea turtles: Three decades of empirical data collected in Atlantic Europe and the Mediterranean
    Gaëlle Darmon, Marcus Schulz, Marco Matiddi, Ana Liria Loza, Jesús Tomás, et al.
    Marine Pollution Bulletin, 2022
  • Long-Term Monitoring of In-Water Abundance of Juvenile Pelagic Loggerhead Sea Turtles (Caretta caretta): Population Trends in Relation to North Atlantic Oscillation and Nesting
    Thomas Dellinger, Vladimir Zekovic, Marko Radeta
    Frontiers in Marine Science, 2022
    Sea turtles have various life-stages, typically being oceanic foragers as juveniles while shifting to more coastal habitats as they mature. The present study focuses on the least studied and well known of these, the juvenile oceanic life stage for the loggerhead sea turtle,Caretta caretta. Loggerhead sea turtles remain threatened by fisheries and their distribution and habitat change in the North Atlantic remains poorly understood. After hatching and swimming out to sea, turtles spend 7 or more years in the pelagic life stage. Madeira Island has an advantage of being situated in the middle of the North Atlantic developmental habitat for loggerheads originating both from the US, as well as, from Cape Verde and other mixed source rookeries. Understanding the demographics of this oceanic life stage has been described as a research priority. We here present a population trendline and the abundance variation of oceanic stage loggerheads, measured at a single geographic spot in Madeiran waters, over the period of 15 years. We find that the observed loggerhead distribution results from combined effects of physical and biological processes within the North Atlantic. We explore physical phenomena that influence abundance variability, and find that oscillations in climate affect the turtle migrations, as does the population recruitment from the nesting rookeries. For this, we use novel cost-effective census methods that take advantage of platforms of opportunity from the blue ecotourism industry. To study the time series and their correlations we use spectral analysis, a method not commonly used in traditional population assessments, including Wavelet and Fourier Transformations (WT and FFT), and Digital Signal Processing (DSP) techniques. A strong anti-correlation between sea turtle sightings and North Atlantic Oscillation seasonal components was found, which implies that loggerhead sea turtles are less abundant during positive NAO phases. We also detected long period trends in the sighting data which we relate to La Niña and El Niño oscillations. Source rookeries also influenced the sighting data with a time-lag of ~ 7years, which coincides with the average time that turtles spend as oceanic juveniles.
  • Potential of MALDI TOF mass spectrometry for detection and quantification of corticosterone in the blood of loggerhead sea turtles
    Dominika Houdova, Iva Popović, Thomas Dellinger, Maja Nešić, Marijana Petković
    International Journal of Mass Spectrometry, 2022
  • Evidence for trophic differences between live and bycatch oceanic juvenile loggerhead sea turtles
    Cheila Raposo, Ana Rita Patrício, Paulo Catry, Thomas Dellinger, José P. Granadeiro
    Marine Biology, 2019
  • Surface behavior of pelagic juvenile loggerhead sea turtles in the eastern North Atlantic
    Carla Freitas, Rui Caldeira, Thomas Dellinger
    Journal of Experimental Marine Biology and Ecology, 2019
  • Abundance and population structure of Plesionika narval (Fabricius, 1787) in the northeastern Atlantic
    R. Sousa, M. R. Pinho, J. Delgado, A. R. Pinto, M. Biscoito, et al.
    Brazilian Journal of Biology, 2019
  • Foraging behavior of juvenile loggerhead sea turtles in the open ocean: From lévy exploration to area-restricted search
    C Freitas, R Caldeira, J Reis, T Dellinger
    Marine Ecology Progress Series, 2018
  • Prospective study of the fishery of the shrimp Plesionika narval (fabricius, 1787) in the Northeastern Atlantic
    R. Sousa, M. R. Pinho, J. Delgado, M. Biscoito, A. R. Pinto, et al.
    Brazilian Journal of Biology, 2017
  • Larval cestodes infecting the deep-water fish, Cataetyx laticeps (Pisces: Bythitidae) from Madeira Archipelago, Atlantic Ocean
    Graça Costa, Mahnaz Khadem, Thomas Dellinger, Manuel Biscoito, Egberto Melo-Moreira
    Acta Parasitologica, 2016
  • Considerations on the biology of Plesionika narval (Fabricius, 1787) in the northeastern Atlantic
    Turkish Journal of Fisheries and Aquatic Sciences, 2014
  • Blood biochemistry reference values for wild juvenile loggerhead sea turtles (Caretta caretta) from Madeira Archipelago
    Cláudia Delgado, Ana Valente, Isabel Quaresma, Margarida Costa, Thomas Dellinger
    Journal of Wildlife Diseases, 2011
  • Identification of likely foraging habitat of pelagic loggerhead sea turtles (Caretta caretta) in the North Atlantic through analysis of telemetry track sinuosity
    Abigail L. McCarthy, Selina Heppell, Francois Royer, Carla Freitas, Thomas Dellinger
    Progress in Oceanography, 2010
  • Sex ratios of loggerhead sea turtles Caretta caretta during the juvenile pelagic stage
    Cláudia Delgado, Adelino V. M. Canário, Thomas Dellinger
    Marine Biology, 2010
  • Helminth component community of the loggerhead sea turtle, caretta caretta, from madeira archipelago, Portugal
    Ana Luisa Valente, Cláudia Delgado, Cláudia Moreira, Sandra Ferreira, Thomas Dellinger, et al.
    Journal of Parasitology, 2009
  • Influence of methoprene and protein on survival, maturation and sexual performance of male Ceratitis capitata (Diptera: Tephritidae)
    M. J. Faria, R. Pereira, T. Dellinger, P. E. A. Teal
    Journal of Applied Entomology, 2008
  • Gill monogeneans of the chub mackerel, Scomber japonicus from Madeiran waters of the Atlantic Ocean, Portugal
    G. Costa, N. Freitas, T.H. Dellinger, K. MacKenzie
    Journal of Helminthology, 2007
  • Compensatory growth in oceanic loggerhead sea turtles: Response to a stochastic environment
    Karen A. Bjorndal, Alan B. Bolten, Thomas Dellinger, Cláudia Delgado, Helen R. Martins
    Ecology, 2003
  • Intraerythrocytic inclusion bodies in the loggerhead sea turtle Caretta caretta from Madeira
    J.C. Eiras, T. Dellinger, A.J. Davies, G. Costa, A.P. Alves de Matos
    Journal of the Marine Biological Association of the United Kingdom, 2000
  • Fish prey of the sympatric Galapagos fur seals and sea lions: Seasonal variation and niche separation
    Thomas Dellinger, Fritz Trillmich
    Canadian Journal of Zoology, 1999
  • Transatlantic developmental migrations of loggerhead sea turtles demonstrated by mtDNA sequence analysis
    Alan B. Bolten, Karen A. Bjorndal, Helen R. Martins, Thomas Dellinger, Manuel J. Biscoito, et al.
    Ecological Applications, 1998
  • Comparisons of social structure of Columbus crabs living on loggerhead sea turtles and inanimate flotsam
    Thomas Dellinger, John Davenport, Peter Wirtz
    Journal of the Marine Biological Association of the United Kingdom, 1997