Research Articles (Mammal Research Institute)

Permanent URI for this collectionhttp://hdl.handle.net/2263/5233

A collection containing some of the full text peer-reviewed/ refereed articles published by researchers from the Mammal Research Institute

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Reproductive females of a cooperatively breeding rodent are in better body condition when living in large groups
Finn, K.T.; Janse van Vuuren, Andries Koch; Suess, Tobias; Hart, Daniel William; Bennett, Nigel Charles; Zottl, M. (Wiley, 2025-07)
Cooperation and group living have been suggested to facilitate survival in varying environments and under challenging conditions. However, group living may also be associated with costs, particularly in species where individuals within groups may compete for limited resources. The costs and benefits of cooperative group living on cooperatively breeding mammals in varying environments remain unclear. Here, we use data collected from wild, cooperatively breeding Natal mole-rats (Cryptomys hottentotus natalensis) inhabiting a seasonally varying environment to assess whether body condition changes between seasons and whether these changes are contingent upon group size. We demonstrate that the body condition of reproductive females improved with increasing helper number during both the benign summer and the harsher winter seasons. However, the body condition of other group members showed little dependency on group size or season. Only when including one extremely large group did the body condition of non-breeders weakly, albeit significantly, change depending on group size and seasonality. These results suggest that larger group sizes may yield some benefits for non-breeding group members during winter and may invoke some costs during summer. Group living in Natal mole-rats is likely promoted by a combination of collective foraging, thermoregulatory benefits, and potentially some indirect fitness benefits through improved body condition of the breeding female.
Fertility up in flames : reduced fertility indices as a consequence of a simulated heatwave on small African mammals
Jacobs, Paul Juan; Bennett, Nigel Charles; Du Plessis, L.; Hart, Daniel William (Wiley, 2025-03)
With the increasing frequency and intensity of heatwaves due to climate change, the survival and reproductive success of mammals could be under significant threat. However, the specific effects of these environmental stressors on mammalian reproductive fitness remain insufficiently explored. This study investigates the impact of a simulated heatwave on male fertility indices in two African rodent species: the mesic four-striped field mouse (Rhabdomys dilectus) and the Namaqua rock mouse (Micaelamys namaquensis) during the breeding season. We measured key indicators of male fertility, including testes mass, testes volume, seminiferous tubule diameter, the presence of sperm, and plasma testosterone levels. Our findings reveal that both species experienced significant effects on male fertility indices, with the smaller R. dilectus showing a decline in all fertility indices following a simulated heatwave. These results suggest that the projected increase in heatwave events may compromise the reproductive success of small mammals, potentially leading to population declines. Finally, this study highlights the need for focused studies on the effect of heatwaves on long-term reproductive success in both males and females.
Examining alterations in fGCM concentrations post-defaecation across three animal feeding classes (ruminants, hindgut fermenters and carnivores)
Osburn, Kayla Rae; Crossey, Bruce Gareth; Majelantle, Tshepiso Lesedi; Ganswindt, Andre (Wiley, 2025-05)
Quantification of faecal glucocorticoid metabolites (fGCMs) is a popular non-invasive technique for monitoring wildlife's response to stressors, demanding an understanding of the stability of fGCM concentrations post-defaecation to ensure comparability of determined fGCM values across samples. To provide species-specific recommendations for the duration within which sampling can take place, we measured the rate at which the fGCM concentrations of nine different species changed throughout a 7-day period post-defaecation. In this study, we explored the temporal dynamics of fGCM concentrations in nine species across three feeding classes (ruminants, hindgut fermenters and carnivores): impala (Aepyceros melampus), giraffe (Giraffa camelopardalis), blue wildebeest (Connochaetes taurinus), plains zebra (Equus quagga), African elephant (Loxodonta africana), white rhino (Ceratotherium simum), cheetah (Acinonyx jubatus), spotted hyena (Crocuta crocuta) and leopard (Panthera pardus). Utilizing enzyme immunoassays already established for each of the focal species, we identified broader feeding class-specific patterns. All herbivores exhibited a significant decrease in fGCM concentrations over time, starting from 6 h (impala) to 48 h (giraffe, blue wildebeest, white rhino and African elephant) post-defaecation. For carnivores, concentrations remained fairly comparable for 12–24 h, after which fGCM concentrations either decreased (spotted hyena), increased (leopard) or remained stable (cheetah), with notable variation in triplicate concentrations (cheetah and leopard). These findings offer insights into scheduling faecal sampling for endocrine monitoring, particularly from free-roaming wildlife, to ensure comparability of determined hormone metabolite concentrations. Furthermore, the species-specific variation in fGCM concentration post-defaecation demonstrated in this study underlines the necessity to investigate every new species to ensure accurate and comparable results. Future studies ought to investigate how the mass of collected material, sex and drying methodologies affect the measurement of fGCMs post-defaecation.
Endemic plants and animals are susceptible to extinction in an imperilled alpine hotspot in southern Africa
Taylor, Peter J.; Bredenhand, Emile; Monadjem, Ara; Armstrong, Adrian J.; Rakotoarivelo, Andrinajoro R.; Mdluli, Veli Monday; Howard, Alexandra; Modise, Serero; Motitsoe, Samuel N.; Ntloko, Pindiwe; Kirkaldy, Abigail P.; Kleynhans, Dewald J.; Jankielsohn, Astrid; Mosikidi, Toka; Oosthuizen, Maria Kathleen; Payne, Stephanie; Munyai, Thinandavha C.; Carbutt, Clinton; Ramoejane, Mpho; Bereng, Mosiuoa; Stiller, Michael; Haddad, Charles R.; Steenhuisen, Sandy-Lynn; Mlambo, Musa C.; Moyo, Sibusisiwe; Nyembe, Nthatisi I.; Mofokeng, Lehlohonolo; Van As, Johann; Malekana, Lesego; Daniel, Gimo M.; Gwate, Onalenna; Van As, Michelle; Harrison, James Du Guesclin; Thabethe, Nokubonga F.; Kheswa, Nozipho; Moloi, Karabo; Sishange, Nkanyiso; Clark, V. Ralph (South African National Biodiversity Institute, 2025-11)
BACKGROUND : As global temperatures rise, alpine species at the upper limit of their distribution are at risk of decline and extinction due to shrinking habitats downslope. The alpine (> 2 800 m a.s.l.) biodiversity of the Maloti-Drakensberg is poorly known but may be threatened by climate change. OBJECTIVES : Using expert BioBlitzes, we documented species richness and elevational patterns of distribution in 14 plant and animal higher taxa from alpine and upper-montane zones in an unexplored corner of the Maloti-Drakensberg. METHODS : Using standardised methods such as Sherman traps, acoustic monitoring, bird timed counts, pitfall traps, sweep nets, aquatic SASS5 kick-nets, timed searches and herbarium collections, we assessed elevational zonation of flowering plant and selected invertebrate and vertebrate diversity in the Witsieshoek Community Conservation Area (WCCA). RESULTS : GBIF records complemented expert BioBlitz data, together enumerating 1 216 plant, vertebrate and invertebrate species along an elevation gradient from 1 760 m to 3 145 m at WCCA. Birds, insects and plants showed concordant beta diversity patterns from BioBlitz and GBIF data: high turnover compared to nestedness in more sedentary insects and plants, and the opposite in more mobile birds (GBIF data not available for bats). Although identifications are ongoing, 17% of species or morphospecies were exclusively recorded in the alpine zone, including 82 species of plants and 92 of animals. CONCLUSION : Alpine endemics are vulnerable to the ‘escalator to extinction’ process due to climate change. Surveys of under-explored alpine hotspots should be prioritised, drawing on mountain tourism-based citizen science. We advocate an ecotourism- and community-centred, restoration and rewilding approach for this strategic and biodiverse community conservation area.
Exploring emotional attachment to non-traditional pets using the Lexington Attachment to Pets Scale (LAPS)
Sturgeon, Diane J.E.; Steele, Zachary T.; Pienaar, Elizabeth Frances (Routledge, 2026)
The growing popularity of non-traditional pets, including reptiles, amphibians, fish, insects, and arachnids, raises important questions about owner attachment and animal welfare. We assessed emotional attachment among US non-traditional pet owners using the Lexington Attachment to Pets Scale (LAPS). An online survey of 1,218 adult pet owners was conducted between 2018 and 2021 through both targeted recruitment (rescue groups, permit holders, herpetological societies) and general population sampling. The LAPS demonstrated excellent internal consistency when applied to non-traditional pets, supporting its cross-taxon validity. Owners of multiple taxa of pets reported significantly higher attachment scores than owners of a single taxon. Linear regression models revealed higher attachment among female respondents and those who personally chose to acquire their pets. Conversely, attachment was lower among older respondents, those with higher incomes, and single-taxon owners who exclusively owned non-traditional pets. Our results underscore the importance of considering owner demographics and motivations for acquiring pets when designing pet welfare interventions and targeted education for non-traditional pet owners.
Metabolic expenditure of submaximal locomotion in naked mole-rats (Heterocephalus glaber) and Damaraland mole-rats
Thirkell, Jack E.; Bennett, Nigel Charles; Hart, Daniel William; Faulkes, Chris G.; Daley, Monica A.; Portugal, Steven J. (Company of Biologists, 2025-06)
Despite extensive studies on the physiology of subterranean rodents, there is comparatively little work documenting the energetics specifically associated with their locomotory energetics. The energetic cost associated with burrowing is great and, in part, explains why subterranean species often maintain their burrows and tunnels across generations. Indeed, the digging metabolic rate of five African mole-rats has been determined to be between three and five times higher than their respective resting metabolic rate, yet the energetic cost of non-digging locomotion (i.e. walking) has not been recorded. Digging in most subterranean species tends to lead to specialisation of the forelimbs and teeth, which may significantly affect the energetic cost associated with non-digging locomotion. Unlike many comparably sized burrowing and tunnelling mammals, African mole-rats appear, superficially at least, to have almost identical forelimbs and hindlimbs. This study explored the locomotory energetics associated with sustained submaximal locomotion (i.e. fast walking; 10 cm s−1) in two African mole-rat species (Fukomys damarensis and Heterocephalus glaber), utilising open-flow respirometry and a small animal treadmill. The mean locomotory energetic rate for F. damarensis was a near 1-fold increase (91.4%) above resting metabolic rate and a 2-fold increase (203.2%) for H. glaber. Net cost of transport was higher overall for H. glaber (2.9±0.6 ml O2 kg−1 m−1) than for F. damarensis (2.4±0.5 ml O2 kg−1 m−1). A trade-off likely exists between limb specialisation for digging and economic locomotion, and thus for most obligately subterranean species, locomotion represents an energetic investment.
Strength in numbers : group size enhances individual survival and colony longevity in Damaraland mole-rats Fukomys damarensis
Jacobs, Paul Juan; Hart, Daniel William; Jarvis, Jennifer U.M.; Bennett, Nigel Charles (Elsevier, 2026-02)
Cooperative behaviour presents an evolutionary paradox because although dispersal may increase direct fitness, many individuals forego reproduction to assist others. In arid-dwelling subterranean mammals, the high energetic costs of underground foraging, together with scarce and patchily distributed food resources are thought to have favoured the evolution of group living and cooperative breeding. These social systems are believed to enhance foraging efficiency and improve the survival prospects of individuals and groups. Using a longitudinal dataset from a wild population of Damaraland mole-rats (Fukomys damarensis) in arid central Namibia, we examine how group size predicts survival and persistence at both the individual and group levels. Our findings show that larger groups confer significant apparent survival benefits, that is the probability that an individual survives and remains available for recapture or resighting, reflecting both true survival and site fidelity, and also enhance colony persistence relative to solitary animals or pairs. We further demonstrate that these very small social-unit states are inherently unstable as without increases in group size, they are unlikely to persist within the population for extended periods. Larger groups clearly enhance survival, making remaining in the natal colony more beneficial than dispersing in an arid environment where dispersal is highly risky. HIGHLIGHTS • Dispersal is risky for Damaraland mole-rats in arid environments. • Solitary individuals and pairs did not persist for an extended period in the same state. • Larger group sizes provide survival benefits for individuals and for colonies.
Large herbivores are linked to higher herbaceous plant diversity and functional redundancy across spatial scales
Trepel, Jonas; Atkinson, Joe; Le Roux, Elizabeth; Abraham, Andrew J.; Aucamp, Margerie; Greve, Michelle; Greyling, Marilize; Kalwij, Jesse M.; Khosa, Steven; Lindenthal, Lukas; Makofane, Caroline; Mokoena, Londiwe; Oosthuizen, Anika; Rech, Bent J.; Lundgren, Erick; Svenning, Jens-Christian; Buitenwerf, Robert (Wiley, 2026-01)
Large herbivores can strongly influence plant communities. However, these effects are highly variable, potentially depending on the herbivore regime, that is, herbivore diversity and density. However, the role of the herbivore regime has been challenging to evaluate across spatial scales due to widespread defaunation and a lack of data on herbivore communities and their densities. Here, we investigated the effects of large herbivores along a gradient of trophic complexity (low to high herbivore diversity) and herbivory intensity (estimated from herbivore biomass and visitation frequency) on plant taxonomic and functional diversity at different scales (plot [n = 250], site [n = 50] and landscape [n = 10]) in 10 reserves in the savanna biome in South Africa. We found higher total plant species richness, driven by higher herbaceous (but not woody) plant species richness, in areas with higher herbivory intensity across multiple scales. While herbivores had no significant relationship with plant functional richness, we observed higher functional redundancy at all scales in areas more frequently visited by herbivores. Overall, herbivore–vegetation relationships were largely consistent across scales, and the strongest effects emerged at the largest scale. Our results show a positive relationship between large herbivores and both herbaceous plant species richness and plant functional redundancy, the latter suggesting higher vegetation resilience (the capacity of ecosystems to quickly recover from disturbances as different species compensate for the loss or decline of others). These effects are largely consistent across scales, indicating that the impact of herbivore regimes on plant communities is predominantly scale-independent and that large herbivores drive vegetation dynamics at both local and large scales. However, the stronger effects observed at the landscape scale imply that herbivore impacts manifest most prominently at larger scales. Altogether, our results suggest that restoring large herbivore populations can be expected to promote herbaceous plant diversity and ecosystem resilience.
Breeding male mole-rats (Fukomys) use strong bites to defend reproductive monopoly
Sumbera, Radim; Kraus, Andrea; Mikula, Ondrej; Okrouhlik, Jan; Measey, John; Begall, Sabine; Bennett, Nigel Charles; Zottl, Markus; Herrel, Anthony; Lovy, Matej (Nature Research, 2026-01)
Bite force is a simple trait indicating an animal’s performance related to foraging, social dominance, and defence, all of which influence individual reproductive success. We examine the effect of breeding status on bite force in four social species of Fukomys, a genus of subterranean African rodents (Bathyergidae). These species are cooperative breeders, where reproduction is limited typically to a breeding pair. We collected in vivo bite force data, head width, and upper incisors width from 404 individuals from 75 families and tested whether breeders exhibit stronger bite force. We reveal that breeding males of all four species outperform non-breeders, with bite force in non-breeding males and females being 12% and 22% lower, respectively. In contrast, breeding females underperform relative to other categories, with bite force approximately 31% lower than in breeding males, and many are reluctant to bite. Head width and upper incisors width corroborate these findings. We propose that breeding males require a stronger bite force because of repeated competition with non-related males that may try to enter the family. In contrast, there is much less competition for the breeding position among females, as females rarely intrude into established families.
Does the public value ecosystem services secured by pine savanna restoration and bobwhite management on private lands?
Nimlos, Nicole M.; Pienaar, Elizabeth Frances; Martin, James A. (Elsevier, 2026-03)
Private land stewardship in the southeastern United States is crucial to attain pine savanna restoration and conservation of the threatened northern bobwhite (Colinus virginianus). Both government and privately funded conservation efforts secure numerous ecosystem services, including groundwater recharge, scenic open spaces, and biodiversity. Yet, we have incomplete information on whether the public values these ecosystem services. From June 15th to July 19th, 2022, we administered stated preference choice experiment surveys to 770 members of the public in Alabama, Georgia, Florida, and South Carolina to ascertain if the public values ecosystem services provided by pine savanna and bobwhite conservation. We analyzed data using hybrid mixed logit models. Respondents positively valued recovery of threatened bobwhite and gopher tortoise populations and high levels of groundwater recharge and scenic open space. Respondents with higher moral obligations to prevent land use conversion (personal norms, awareness of consequences, and ascription of responsibility related to conservation) were more likely to support allocation of taxes to pine savanna restoration on private lands. Respondents' moral obligation to prevent land use conversion was positively correlated with their engagement in outdoor recreational activities. Our findings indicate that the public values pine savanna and bobwhite conservation efforts on private lands in the Southeast, and that outreach related to pine savanna restoration efforts should appeal to people's moral obligation to support conservation of biodiversity, habitat restoration, and the provision of ecosystem services. HIGHLIGHTS • We use hybrid mixed logit models to analyze preferences for pine savanna restoration. • Moral obligation to prevent land use conversion depends on political orientation. • Recreational activities and moral obligation influence support for restoration programs. • Respondents placed greatest value on bobwhite recovery and high groundwater recharge.
Comparing seismic survey mitigation regulations : lessons for South Africa from international frameworks
Purdon, Jean; Somers, Michael J.; Shabangu, Fannie Welcome; Doh, Y.; Scheun, J. (Taylor and Francis, 2025-11-24)
Underwater seismic surveys generate high-intensity, low-frequency noise that can negatively affect a range of marine fauna. As a result, countries have implemented mitigation regulations to reduce the potential impacts of this activity. This study examines seismic survey mitigation regulations from Australia, the United States, Brazil, New Zealand, Canada and the United Kingdom, and compares them with the current regulations in South Africa. We focused on setting the radii of exclusion zones, ‘soft-start’ procedures, passive acoustic monitoring, marine mammal observer qualifications and standards, and regulatory oversight. Of the six countries reviewed, Australia and New Zealand have implemented the most robust mitigation measures. Furthermore, Australia stands out for its independent regulatory authority overseeing offshore environmental compliance. We recommend the establishment of an independent regulatory board in South Africa to oversee the development of environmental impact assessment guidelines and mitigation protocols. By adopting these measures and aligning with international best practice, South Africa could become a regional, if not global, leader in science-based environmental regulation and the protection of marine fauna from seismic surveys.
Exported illegally, threatened locally : South Africa in the global reptile pet trade
Willoughby, Sian; Selier, SA Jeanetta; Zondi, Zwelakhe; Hall, Grant (Taylor and Francis, 2025)
The global illegal exotic pet trade is a major driver of biodiversity loss, particularly affecting reptile species listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. CITES is an international agreement used to monitor the import and export of listed fauna and flora, ensuring trade is not detrimental to the survival of listed species in the wild. This study investigates South Africa’s role in the international trade of reptiles, using the endemic Sungazer lizard (Smaug giganteus) as a case study. Analysis of CITES Trade Database records reveals systemic reporting in accuracies, including discrepancies between importer and exporter data, misuse of source and purpose codes, and evidence of wildlife laundering. Trade peaks in 1988 and 2013 correspond to increased species visibility due to CITES listing and cultural associations with popular media, respectively, illustrating the influence of anthropogenic and media-driven factors on global wildlife trade demand. Evidence of potentially illegal exports from non-range countries and suspicious declarations of captive-bred specimens suggests that South Africa may be both a source and transit country in illicit reptile trade networks. The lack of enforcement, coupled with the ease of smuggling, exacerbates the threat to S. giganteus and similar threatened reptile species. These findings underscore the urgent need to strengthen CITES data reliability, enforce trade regulations, and enhance protection for South African reptile species vulnerable to overexploitation.
Intensive feeding modifies nutrient patterns in a strictly protected area
Trepel, Jonas; Abraham, Andrew J.; Di Nicola, Walter; Gelin, Uriel; Gahbauer, Martin; Heurich, Marco; Le Roux, Elizabeth (Elsevier, 2025-09)
Recovering deer populations are causing conflict across Europe, especially in the vicinity of protected areas where densities are generally higher. Consequently, a variety of management approaches, such as the provision of winter feeding, have been deployed to keep deer from foraging in undesired areas in an attempt to mitigate conflicts. However, as large ungulates play a key role in nutrient recycling and redistribution, management actions that affect their space use and introduce additional nutrients into a system may translate into changes in the biogeochemistry of protected areas. Yet, little is known about the implications of such deer-management strategies on nutrient patterns. Here, we tested the effects of intensive supplementary feeding in combination with winter enclosures on nutrient distribution in a strictly protected area in Central Europe, the Bavarian Forest National Park. We found significant effects of the current management approach on plant nutrients with elevated nutrient concentrations not only within, but, importantly, extending up to several hundred meters around the enclosures/feeding stations. The increased nutrient concentrations could have cascading consequences for soil microbial activity, plant community composition and other herbivores. Our results illustrate that management actions designed to solve a specific problem (mitigating human-wildlife conflict), may alter local landscape chemistry and influence broader ecosystem functions. Ultimately, this may compromise conservation success, highlighting the need to critically evaluate all potential consequences of common management approaches such as supplementary feeding.
Perspectives on wildlife agency mange management in black bears and other carnivores
Francisco, Raquel; Pienaar, Elizabeth Frances; Yabsley, Michael J. (Wiley, 2026-02)
Sarcoptic mange is an emerging parasitic disease affecting North American black bears (Ursus americanus) and has been increasingly reported since the early 1990s. As mange spreads into naive bear populations, wildlife managers face challenges related to surveillance, interagency coordination, and stakeholder expectations. In 2023, we surveyed 35 state and federal wildlife agency personnel and academic partners to assess management practices for mange, barriers to effective interventions, and how agencies engage with the public and key stakeholders. Respondents represented 17 states, 7 with and 10 without reports of sarcoptic mange in black bears, with over half (51.4%) working in their current institution for more than 10 years. Respondents generally agreed on dispatching severely affected wildlife (97.1%) and monitoring mild to moderate cases. Although respondents supported stakeholder and public reporting of mange cases (71.4%), they opposed stakeholder and public intervention in mange management (e.g., treatment, handling, relocation). Fewer than half of respondents (45.7%) indicated that mange reports are entered into a formal dataset, limiting long-term surveillance and decision-making. Our study highlights the need for a unified multi-state communication framework to increase public support for agency management actions, and the importance of implementing a centralized mange data repository to enhance long-term surveillance of mange and improve response efforts.
Biomass distribution of sympatric mammals in a European temperate forest
Pleskalt, Andro; Farias, Sebastião; Vicedo, Toni; Álvarez-Martínez, Jose Manuel; Roces-Díaz, José Valentín; Meloro, Carlo; Pereira, Soraia; Cruz, Antonio; García, Jesús; Gómez, Pablo; Lamillar, María Ángel; Marsella, Elena; Varas, Manuel Jesús; Álvarez, Elena; Dalerum, Fredrik (The Royal Society, 2025-08)
The distribution of biomass among trophic levels and different types of organisms is a key characteristic of ecosystems. However, such biomass distributions might exhibit large perturbations owing to human activities. We used long-term camera trap data from a temperate forest ecosystem within the Cantabrian range, northern Spain, to quantify the biomass distribution of 10 mammal species ranging in body mass from 300 g to almost 100 kg. The species are representative of three distinct orders and include trophic levels from primary to secondary consumers. The observed biomass distribution was bottom-heavy with a disproportionally low biomass of secondary consumers, in particular large-bodied predators. In addition, the ratio of plant biomass to the biomass of mammalian primary consumers was over 6000 : 1 for total above-ground-plant biomass and over 700 : 1 for plant biomass available for mammal consumption. We suggest that the observed biomass distribution both among mammals and between mammals and plants provide an example of trophic downgrading, and highlight the radical effects human activities might have on the structure of terrestrial ecosystems.
Four decades of annual monitoring reveal declining reproductive success of a migratory baleen whale
Vermeulen, Els; Wilkinson, Christopher; Best, Peter B.; Findlay, Kenneth Pierce (Nature Research, 2025-10-06)
Understanding and mitigating threats to species survival relies on the ability to track key demographic processes over time. Among these processes, reproduction stands out as a primary biological driver of population growth and resilience. Multiple factors affect reproductive success, including environmental variables and resource availability. Long-term trends in reproductive parameters of long-lived species can thus serve as indicators of ecosystem health over meaningful timescales. This study analyses the reproductive performance of southern right whales (Eubalaena australis) in South Africa using forty years of individual sighting histories. Results reveal that the median and average calving intervals increased post-2010, reaching an average maximum of 7.2 years in 2022. The average calving rate decreased significantly across the four decades, from 0.48 calves/year in the 1980s to 0.19 calves/year in the 2010s. Although based on observational data, these findings align with the hypothesis of a trade-off linked to the reduced maternal body condition in this population, likely indicative of diminished foraging success associated with recorded regional Antarctic sea ice declines and reduced prey availability. The study adds to the growing evidence that baleen whale reproduction is influenced by environmental change, reinforcing the need for long-term monitoring to understand population dynamics and their potential role as sentinels of ocean health.
Territoriality in adult male sub-Antarctic fur seals at Gough Island
Bester, Marthan Nieuwoudt; Rossouw, G.J. (Springer, 2025-03)
We analysed unpublished data on territory size and tenure in adult male sub-Antarctic fur seals Arctocephalus tropicalis recorded at Gough Island, Southern Ocean, during the 1975/76 austral summer breeding season. Adult males (n=15) remained on their territories for between 35–56 days (mean 45.4±6.7 days). Territory size during the peak breeding season was 21.9 m2 on average (n=42), but when partitioned by beach type, average territory sizes were 13.8 (n=9), 20.1 (n=17) and 28.3 m2 (n=16). Both territory tenure and territory size fall within the reported range of values established in fur seal species which hold territories on land as the predominant male reproductive strategy. We highlight numerous confounding factors that impact comparative studies which should be considered when interpreting theoretical, conceptual, and modelling approaches about territorial behaviour in otariids.
Seasonal occurrence and condition of leopard seals at an extralimital Sub‑Antarctic Island
Ross, Michael D.; Leitner, Monica; Oosthuizen, W. Chris; Bester, Marthan Nieuwoudt; Jordaan, Rowan Keith; Voysey, Michael D.; Conradie, Everhard C.; Dosi, Banele; Evans, Sean; Lloyd, Kyle J.; Monier, Zafar; Purdon, Jean; Reisinger, Ryan R.; Shihlomule, Yinhla Desmond; Van der Vyver, J.S. Fredrik; De Bruyn, P.J. Nico (Springer, 2025-06)
Leopard seals (Hydrurga leptonyx) occur mainly south of the Antarctic Polar Front, but immatures, in particular, seasonally move beyond this range during the austral winter and spring, typically under increased sea ice conditions. Extralimital occurrences of leopard seals can be observed at several sub-Antarctic islands where they haul out to rest. We present new records of leopard seal sightings at Marion Island, southern Indian Ocean, from 2006 to 2024 and discuss fluctuations in their seasonal and annual abundance (drawing on data collected since 1980) and body condition based on regular surveys. The eastern beaches at Marion Island were surveyed every 7–10 days while the western beaches were visited monthly. Observed leopard seals were photographed and given a body condition score based on the visibility of bony protrusions. From 2006 to 2024, we identified 35 presumed unique immature leopard seals between July and November, with a peak in September, all being immatures. Individuals to which we could assign body condition scores were either in good or excellent condition. This contrasted with the prevailing hypothesis that leopard seal body condition deteriorates with decreasing latitude. However, we could not determine whether this was because of an actual shift in body condition or because we used a different scoring system from other studies. We recommend adopting a standardised scoring system for visually estimating pinniped body condition and a global repository to monitor leopard seal haul-outs. As an apex predator, leopard seals may be important indicators in Antarctic and sub-Antarctic ecosystems, and monitoring changes in their distribution and body condition may indicate environmental and biological changes in these remote regions.
Monitoring of vagrant seals on mid-oceanic islands of the South Atlantic Ocean
Bester, Marthan Nieuwoudt; Somers, Michael J. (Springer, 2025-09)
Extra-limital sightings of seals breeding on the Antarctic pack- and fast ice and on sub-Antarctic and temperate islands of the South Atlantic Ocean are summarised. Particular life history events of four vagrant seal species that have turned up on Mid-Atlantic Ridge islands are presented, and the likely arrival of a further three vagrant seal species is speculated upon. The setting up and/or expansion of a recording system underpinned by an appropriate sighting protocol for vagrant seals in which citizen scientists can participate is advanced. Determination of whether range contractions/expansions of seals in the South Atlantic are taking place reflects on the status of the source population(s). Seal vagrancy may conceivably also be involved in the spread of viral diseases such as highly pathogenic avian influenza and rabies. Insights gained through extra-limital sightings of seals may assist with the establishment of conservation strategies.
Comparative life-cycle analyses reveal interacting climatic and biotic drivers of population responses to climate change
Ickin, Esin; Conquet, Eva; Abrahms, Briana; Albon , Steve D.; Blumstein, Daniel T.; Bond, Monica L.; Boersma , P. Dee; Clark-Wolf, Tyler J.; Clutton-Brock, Tim H.; Compagnoni , ldo; Dostálek, Tomáš; Evers, Sanne M.; Fichtel, Claudia; Gamelon, Marlène; García-Callejas, David; Griesser, Michael; Hansen , Brage B.; Jenouvrier, Stéphanie; Jerstadz, Kurt; Kappeler, Peter M.; Layton-Matthews, Kate; Lee, Derek E.; Lloret, Francisco; Loonen, Maarten J.J.E.; Malchow, Anne-Kathleen; Manser, Marta B.; Martin , Julien G.A.; Morales-González, Ana; Münzbergová, Zuzana; Nater, Chloé R.; Pillay, Neville; Quéroué, Maud; Røstadak, ac,ad, ai,al, am, a and , Ole W.; Sánchez-Mejía, Teresa; Schradin, Carsten; Sæther, Bernt-Erik; Ozgul, Arpat; Paniw, Maria (Oxford University Press, 2025-09)
Responses of natural populations to climate change are driven by how multiple climatic and biotic factors affect survival and reproduction, and ultimately shape population dynamics. Yet, despite substantial progress in synthesizing the sensitivity of populations to climatic variation, comparative studies still overlook such complex interactions among drivers that generate variation in population-level metrics. Here, we use a common framework to synthesize how the joint effects of climate and biotic drivers on different vital rates impact population change, using unique long-term data from 41 species, ranging from trees to primates. We show that simultaneous effects of multiple climatic drivers exacerbate population responses to climate change, especially for fast-lived species. However, accounting for density feedbacks under climate variation buffers the effects of climate change on population dynamics. In all species considered in our analyses, such interactions between climate and density had starkly different effects depending on the age, size, or life-cycle stage of individuals, regardless of the life history of species. Our work provides the first general framework to assess how covarying effects of climate and density across a wide range of population models can impact populations of plants and animals under climate change.

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