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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Southern Ocean food-webs and climate change : a short review and future directions
(Public Library of Science, 2024-03-11) Queiros, Jose P.; Borras-Chavez, Renato; Friscourt, Noemie; Groß, Jasmin; Lewis, Candice B.; Mergard, Georgia; O’Brien, Katie
Food-webs are a critical feature of ecosystems and help us understand how communities will respond to climate change. The Southern Ocean is facing rapid and accelerating changes due to climate change. Though having evolved in an isolated and somewhat extreme environment, Southern Ocean biodiversity and food-webs are among the most vulnerable. Here, we review 1) current knowledge on Southern Ocean food-webs; 2) methods to study foodwebs; 3) assessment of current and future impacts of climate change on Southern Ocean food-webs; 4) knowledge gaps; and 5) the role of Early Career Researchers (ECRs) in future studies. Most knowledge on Southern Ocean food-webs come from the pelagic environment, both at macro- and microbial levels. Modelling and diet studies of individual species are major contributors to the food-web knowledge. These studies revealed a short food-web, predominantly sustained by Antarctic Krill (Euphausia superba). Additionally, alternative pathways exist, involving other krill species, fish, and squid, which play equally important roles in connecting primary producers with top predators. Advantages and disadvantages of several techniques used to study Southern Ocean food-webs were identified, from the classical analyses of stomach contents, scats, or boluses to the most recent approaches such as metabarcoding and trophic-biomarkers. Observations show that climate change can impact the foodweb in different ways. As an example, changes to smaller phytoplankton species can lengthen the food-web, increasing assimilation losses and/or changing nutrient cycles. Future studies need to focus on the benthic-dominated food-webs and the benthopelagic coupling. Furthermore, research during the winter season and below the ice-shelves is needed as these areas may play a crucial role in the functioning of this ecosystem. ECRs can play a significant role in advancing the study of Southern Ocean food-webs due to their willingness for interdisciplinary collaboration and proficiency in employing various methodologies, contributing to the construction of high-resolution food-webs.
Successful alien plant species exhibit functional dissimilarity from natives under varied climatic conditions but not under increased nutrient availability
(Wiley, 2025-03) Milanovic, Marija; Bakker, Jonathan D.; Biederman, Lori; Borer, Elizabeth; Catford, Jane A.; Cleland, Elsa; Hagenah, Nicole; Haider, Sylvia; Harpole, W. Stanley; Komatsu, Kimberly; Macdougall, Andrew S.; Roemermann, Christine; Seabloom, Eric W.; Knapp, Sonja; Kuehn, Ingolf
AIMS : The community composition of native and alien plant species is influenced by the environment (e.g., nutrient addition and changes in temperature or precipitation). A key objective of our study is to understand how differences in the traits of alien and native species vary across diverse environmental conditions. For example, the study examines how changes in nutrient availability affect community composition and functional traits, such as specific leaf area and plant height. Additionally, it seeks to assess the vulnerability of high-nutrient environments, such as grasslands, to alien species colonization and the potential for alien species to surpass natives in abundance. Finally, the study explores how climatic factors, including temperature and precipitation, modulate the relationship between traits and environmental conditions, shaping species success. LOCATION : In our study, we used data from a globally distributed experiment manipulating nutrient supplies in grasslands worldwide (NutNet). METHODS : We investigate how temporal shifts in the abundance of native and alien species are influenced by species-specific functional traits, including specific leaf area (SLA) and leaf nutrient concentrations, as well as by environmental conditions such as climate and nutrient treatments, across 17 study sites. Mixed-effects models were used to assess these relationships. RESULTS : Alien and native species increasing in their abundance did not differ in their leaf traits. We found significantly lower specific leaf area (SLA) with an increase in mean annual temperature and lower leaf Potassium with mean annual precipitation. For trait–environment relationships, when compared to native species, successful aliens exhibited an increase in leaf Phosphorus and a decrease in leaf Potassium with an increase in mean annual precipitation. Finally, aliens' SLA decreased in plots with higher mean annual temperatures. CONCLUSIONS: Therefore, studying the relationship between environment and functional traits may portray grasslands' dynamics better than focusing exclusively on traits of successful species, per se.
Effect of exogenous manipulation of glucocorticoid concentrations on meerkat heart rate, behaviour and vocal production
(Elsevier, 2025-02) Driscoll, Isabel; Briefer, Elodie F.; Ganswindt, Andre; Manser, Marta B.
Encoding of emotional arousal in vocalisations is commonly observed in the animal kingdom, and provides a rapid means of information transfer about an individual's affective responses to internal and external stimuli. As a result, assessing affective arousal-related variation in the acoustic structure of vocalisations can provide insight into how animals perceive both internal and external stimuli, and how this is, in turn, communicated to con- or heterospecifics. However, the underlying physiological mechanisms driving arousal-related acoustic variation remains unclear. One potential driver of such variation in behaviour and vocal production are glucocorticoids. Through exogenous glucocorticoid manipulation, we aimed to gain insight on the relationship between arousal and physiological parameters, behaviour and vocal production in wild meerkats (Suricata suricatta). To this aim, we administered glucocorticoids to wild meerkats, and recorded their heart rate, vigilance behaviour, call rate and acoustic structure during natural behavioural contexts. The results suggest that, although the glucocorticoid treatment did increase plasma glucocorticoid levels, this did not result in observable changes in heart rate, vigilance, or vocal production. This lack of treatment effect suggests that, while glucocorticoids may be a significant component and correlate of the arousal response, they are not the direct drivers of affective arousal related changes in heart rate, behaviour, or vocal production.
Feeding through the ages : revisiting the diet of meerkats
(Elsevier, 2025-03) Jubber, Walter R.; Manser, Marta B.; Fuller, Andrea
We investigated the diet and foraging behaviour of a social carnivore, the meerkat (Suricata suricatta), living in stochastic dryland, and examined seasonal, as well as age-related variation in diet. Insecta constituted the highest percentage of prey eaten (88.4%), followed by Arachnida (5.7%), Diplopoda (4.3%), and Reptilia (1.1%). Within Insecta, Coleoptera (70.4%) was the most dominant prey order in the diet, followed by Lepidoptera and Hymenoptera. There was seasonal variation in the diet of meerkats, with the three main Coleoptera families eaten year-round, but higher consumption of Coleoptera adults in the wet season than in the dry season. We found that old adult meerkats (>24 months) consumed the most large-sized prey, while sub-adults (6–10 months) had the highest prey count of small adult Carabidae beetles. Yearlings (15–24 months) ate the highest percentage of Hepialidae caterpillars. Whether the high representation of Coleoptera in the meerkat diet reflects dietary opportunism associated with the relatively high abundance of Coleoptera, or specialisation in the diet regardless of abundance, remains to be determined.
The challenges, opportunities and future of comparative physiology in the Global South : perspectives of early-career researchers
(Company of Biologists, 2024-10) Bars-Closel, Melissa; Capparelli, Mariana V.; Conradie, Shannon R.; Diele-Viegas, Luisa Maria; Donaldson, Ashleigh C.; Kosmala, Georgia K.; Madelaire, Carla B.; De Mello, Daniela M.D.; Majelantle, Tshepiso L.; Martins, Mariana F.; Moreira, Daniel C.; Ngcamphalala, Celiwe A.; Noakes, Matthew J.; Shankar, Anusha; Webster, Andrea B.
Researchers in the Global South (GS, developing countries) make valuable contributions to the field of comparative physiology, but face economic and scientific disparities and several unique challenges compared with colleagues in the Global North (developed countries). This Perspective highlights some of the challenges, knowledge gaps and disparities in opportunity faced by GS researchers, especially those at early-career stages. We propose collaborative solutions to help address these issues, and advocate for promoting investment and cultural and societal change for a more inclusive research community. Additionally, we highlight the role of GS researchers in contributing expert knowledge on local biodiversity and the environment; this knowledge can help to shape the future of comparative physiology, allowing us to achieve a better understanding of the evolution of physiological mechanisms and to develop innovative solutions to environmental and biomedical challenges. With this Perspective, we hope to highlight the need to foster a more diverse, equitable and inclusive research landscape in comparative physiology; one that empowers GS scientists to address the global challenges associated with biodiversity loss, climate change and environmental pollution.
Light sensitivity of the circadian system in the social highveld mole-rat Cryptomys hottentotus pretoriae
(Company of Biologists, 2024-09) Chanel, Pauline N.C.; Bennett, Nigel C.; Oosthuizen, Maria Kathleen
Highveld mole-rats (Cryptomys hottentotus pretoriae) are social rodents that inhabit networks of subterranean tunnels. In their natural environment, they are rarely exposed to light, and consequently their visual systems have regressed over evolutionary time. However, in the laboratory they display nocturnal activity, suggesting that they are sensitive to changes in ambient illumination. We examined the robustness of the Highveld mole-rat circadian system by assessing its locomotor activity under decreasing light intensities. Mole-rats were subjected to seven consecutive light cycles commencing with a control cycle (overhead fluorescent lighting at 150 lx), followed by decreasing LED lighting (500, 300, 100, 10 and 1 lx) on a 12 h light:12 h dark (L:D) photoperiod and finally a constant darkness (DD) cycle. Mole-rats displayed nocturnal activity under the whole range of experimental lighting conditions, with a distinct spike in activity at the end of the dark phase in all cycles. The mole-rats were least active during the control cycle under fluorescent light, locomotor activity increased steadily with decreasing LED light intensities, and the highest activity was exhibited when the light was completely removed. In constant darkness, mole-rats displayed free-running rhythms with periods (τ) ranging from 23.77 to 24.38 h, but was overall very close to 24 h at 24.07 h. Our findings confirm that the Highveld mole-rat has a higher threshold for light compared with aboveground dwelling rodents, which is congruent with previous neurological findings, and has implications for behavioural rhythms.
Evolutionary shifts in the thermal biology of a subterranean mammal : the effect of habitat aridity
(Company of Biologists, 2024-12) Merchant, Hana N.; Hart, Daniel William; Bennett, Nigel C.; Janse van Vuuren, Andries Koch; Freeman, Marc Trevor; McKechnie, Andrew E.; Faulkes, Chris G.; Mordaunt, Nathan D.; Portugal, Steven J.
Subterranean mammals representing a single subspecies occurring along an aridity gradient provide an appropriate model for investigating adaptive variation in thermal physiology with varying levels of precipitation and air temperature. This study examined the thermal physiological adaptations of common mole-rats (Cryptomys hottentotus hottentotus) across five populations along an aridity gradient, challenging the expectation that increased aridity would lead to reduced metabolic rate, lower body temperatures and broader thermoneutral zones. No significant, consistent differences in metabolic rate, body temperature or thermal conductance were observed between populations, suggesting uniform thermoregulatory mechanisms across habitats. Instead, behavioural strategies such as huddling and torpor may play a more prominent role than physiological adaptations in managing temperature regulation and water balance. The study also observed osmoregulatory differences, with populations employing distinct behavioural cooling strategies in response to water availability. These results underscore the need for further research into the responses of subterranean species to climate change, particularly in understanding how increasing global temperatures and aridification might influence species distribution if they lack the physiological capacity to adapt to future climatic conditions.
Contest competition and injury in adult male sub-Antarctic fur seals
(Springer, 2024-05) Bester, Marthan Nieuwoudt; Rossouw, G.J.; Van Staden, Paul Jacobus; mnbester@zoology.up.ac.za
We recorded intra-sexual behaviour of adult male sub-Antarctic fur seals Arctocephalus tropicalis at Gough Island, Southern Ocean, during the 1975/76 summer breeding season. Our re-analysed data address male ‘contest competition’, which relates to the costs of intra-sexual disputes, including fights. We considered the risks/benefits of fighting through investigation of injuries (n = 353) sustained by adult males (n = 124) in fights. Injuries were predominantly on the forequarters, especially around the insertion areas of the front flippers (41%) with its sparse pelage, compared to the neck and chest areas combined (29%), an area which is well protected by thick pelage. The infliction of serious, sometimes debilitating, injuries to competitors increases a male’s access to females. Injuries predominate in injured, defeated males that gather at non-breeding sites, suggesting that injuries inflicted by dominant males were successful in excluding competing males from breeding sites.
Use of acoustic signals in Cape fur seal mother–pup reunions : individual signature, signal propagation and pup home range
(Company of Biologists, 2024-07) Martin, Mathilde; Gridley, Tess; Immerz, Antonia; Elwen, Simon H.; Charrier, Isabelle
The Cape fur seal (Arctocephalus pusillus pusillus) is one of the most colonial mammals, with colonies of up to hundreds of thousands of individuals during the breeding season. During the lactation period, mothers and pups are regularly separated as females undertake multiday foraging trips at sea. Mothers and pups use a mutual vocal recognition system to reunite after separation. Such communication is highly constrained by both high background noise and risk of individual confusion owing to the density of seals. This study aimed to experimentally assess the acoustic features relevant for mother–pup vocal identification and the propagation properties of their calls. Playback experiments revealed that mother and pup individual vocal signatures rely on both temporal and frequency parameters: amplitude and frequencymodulations, timbre and fundamental frequency (f0). This is more parameters than in any colonial species studied so far. The combinational use of acoustic features reinforces the concept that both environmental and social constraints may have acted as selective pressures on the individual vocal recognition systems. Theoretical propagation distances of mother and pup vocalisations were estimated to be below the range of distances at which mother–pup reunions can occur. This suggests that Cape fur seals may have strong abilities to extract vocal signals from the background noise, as previously demonstrated in the highly colonial king penguin. Investigating the transmission of information throughout the propagation of the signal as well as the ability of the receiving individual to decipher vocal signatures is crucial to understanding vocal recognition systems in the wild.
A mouse in the spotlight : response capacity to artificial light at night in a rodent pest species, the southern multimammate mouse (Mastomys coucha)
(Elsevier, 2024-12) Oosthuizen, Tasha; Pillay, Neville; Oosthuizen, Maria Kathleen; moosthuizen@zoology.up.ac.za
Multimammate mice are prolific breeders, can cause significant agricultural damage, and are reservoir hosts for a number of pathogens. They are nocturnal and given their success in urbanised rural environments, we were interested in how they would respond to increasingly bright anthropogenic spaces. We evaluated the locomotor activity of southern multimammate mice (Mastomys coucha), under four treatments: in an outdoor enclosure with natural light and temperature fluctuations, in a laboratory under a standard light regime, and two artificial light at night (ALAN) regimes (2 Lux) of varying proximity. The study animals remained nocturnal for the duration of the experiments. They were more active under the laboratory conditions with lower day-time light levels compared to the outdoor treatment but reduced their activity under ALAN. When the night light originated remotely, activity levels decreased by more than 50%, whereas under direct ALAN from above the cages, there was a 75% decrease in activity. The onset of activity was later during the two LAN treatments. We concluded that Mastomys coucha is strongly averse to light and show severe behavioural and circadian responses to light at night. We predict that it is unlikely that Mastomys will flourish in cities, but that they could thrive in and around dark urbanised refugia.
A frog in hot water : the effect of temperature elevation on the adrenal stress response of an African amphibian
(PeerJ Inc., 2024-08) Scheun, Juan; Venter, Leanne; Ganswindt, Andre
Amphibians, with their unique physiology and habitat requirements, are especially vulnerable to changes in environmental temperatures. While the activation of the physiological stress response can help to mitigate the impact of such habitat alteration, chronic production of elevated glucocorticoid levels can be deleterious in nature. There is no empirical evidence indicating the physiological response of African amphibians to temperature changes, where individuals are unable to emigrate away from potential stressors. To rectify this, we used the edible bullfrog (Pyxicephalus edulis) as a model species to determine the effect of elevated temperature on the adrenocortical response of the species using a recently established matrix. While a control group was kept at a constant temperature (25 ◦C) throughout the study period, an experimental group was exposed to control (25 ◦C) and elevated temperatures (30 ◦C). Mucous swabs were collected throughout the study period to determine dermal glucocorticoid (dGC) concentrations, as a proxy for physiological stress. In addition to this, individual body mass measurements were collected. The results showed that individuals within the experimental group who experienced increased temperatures had significantly elevated dGC levels compared to the control animals. Furthermore, there was a significant difference in the percentage mass change between experimental and control animals . These findings indicate the physiological sensitivity of the edible bullfrog to a thermal stressor in captivity. While this study shows the importance of proper amphibian management within the captive environment, it also highlights the coming danger of global climate change to this and similar amphibian species.
Genome sequencing of historical encephalomyocarditis viruses from South Africa links the historical 1993/4 savanna elephant (Loxodonta africana) outbreak to cryptic mastomys rodents
(MDPI, 2024-03) Van Meer, Vanessa; Paweska, Janusz Tadeusz; Swanepoel, Robert; Grobbelaar, Antoinette; Bastos, Armanda D.S.; armanda.bastos@up.ac.za
From 1993 to 1994, 64 free-ranging elephants (Loxodonta africana) succumbed to encephalomyocarditis in the Kruger National Park, South Africa, of which 83% were adult bulls. Mastomys rodents were implicated as the reservoir host of the Encephalomyocarditis virus (EMCV) based on serology and RT-PCR. However, in the absence of sequence-confirmation of both the virus and the rodent host, definitive links between the elephant outbreak strains and rodent reservoir could not be established. In this study, we generate the first reference genome sequences for three historical EMCVs isolated from two Mastomys rodents and one Mastomys-associated mite, Laelaps muricola, in Gauteng Province, South Africa, in 1961. In addition, near-complete genome sequences were generated for two elephant outbreak virus strains, for which data were previously limited to the P1 and 3D genome regions. The consensus sequence of each virus was determined using a PCRSanger sequencing approach. Phylogenetic analysis confirmed the three near-identical (99.95–99.97%) Mastomys-associated viruses to be sister to the two near-identical (99.85%) elephant outbreak strains, differing from each other at 6.4% of sites across the ~7400-nucleotide region characterised. This study demonstrates a link between Mastomys-associated viruses and the historical elephant outbreak strains and implicates Mastomys as reservoirs of EMCV in South Africa.
Where do core thalamocortical axons terminate in mammalian neocortex when there is no cytoarchitecturally distinct layer 4?
(Wiley, 2024-07) Bhagwandin, Adhil; Molnar, Zoltan; Bertelsen, Mads F.; Karlsson, Karl Æ.; Alagaili, Abdulaziz N.; Bennett, Nigel Charles; Hof, Patrick R.; Kaswera-Kyamakya, Consolate; Gilissen, Emmanuel; Jayakumar, Jaikishan; Manger, Paul R.
Although the mammalian cerebral cortex is most often described as a hexalaminar structure, there are cortical areas (primary motor cortex) and species (elephants, cetaceans, and hippopotami), where a cytoarchitecturally indistinct, or absent, layer 4 is noted. Thalamocortical projections from the core, or first order, thalamic system terminate primarily in layers 4/inner 3. We explored the termination sites of core thalamocortical projections in cortical areas and in species where there is no cytoarchitecturally distinct layer 4 using the immunolocalization of vesicular glutamate transporter 2, a known marker of core thalamocortical axon terminals, in 31 mammal species spanning the eutherian radiation. Several variations from the canonical cortical column outline of layer 4 and core thalamocortical inputs were noted. In shrews/microchiropterans, layer 4 was present, but many core thalamocortical projections terminated in layer 1 in addition to layers 4 and inner 3. In primate primary visual cortex, the sublaminated layer 4 was associated with a specialized core thalamocortical projection pattern. In primate primary motor cortex, no cytoarchitecturally distinct layer 4 was evident and the core thalamocortical projections terminated throughout layer 3. In the African elephant, cetaceans, and river hippopotamus, no cytoarchitecturally distinct layer 4 was observed and core thalamocortical projections terminated primarily in inner layer 3 and less densely in outer layer 3. These findings are contextualized in terms of cortical processing, perception, and the evolutionary trajectory leading to an indistinct or absent cortical layer 4.
Timely questions emerging in chronobiology : the circadian clock keeps on ticking
(Ubiquity Press, 2024-04-02) Chawla, Sangeeta; O'Neill, John; Knight, Marina I.; He, Yuqing; Wang, Lei; Maronde, Erik; Rodriguez, Sergio Gil; Van Ooijen, Gerben; Garbarino-Pico, Eduardo; Wolf, Eva; Dkhissi-Benyahya, Ouria; Nikhat, Anjoom; Ckakrabarti, Shaon; Youngstedt, Shawn D.; Mak, Natalie Zi-ching; Provencio, Ignacio; Oster, Henrik; Goel, Namni; Caba, Mario; Oosthuizen, Maria Kathleen; Duffield, Giles E.; Chabot, Christopher; Davis, Seth J.
Chronobiology investigations have revealed much about cellular and physiological clockworks but we are far from having a complete mechanistic understanding of the physiological and ecological implications. Here we present some unresolved questions in circadian biology research as posed by the editorial staff and guest contributors to the Journal of Circadian Rhythms. This collection of ideas is not meant to be comprehensive but does reveal the breadth of our observations on emerging trends in chronobiology and circadian biology. It is amazing what could be achieved with various expected innovations in technologies, techniques, and mathematical tools that are being developed. We fully expect strengthening mechanistic work will be linked to health care and environmental understandings of circadian function. Now that most clock genes are known, linking these to physiological, metabolic, and developmental traits requires investigations from the single molecule to the terrestrial ecological scales. Real answers are expected for these questions over the next decade. Where are the circadian clocks at a cellular level? How are clocks coupled cellularly to generate organism level outcomes? How do communities of circadian organisms rhythmically interact with each other? In what way does the natural genetic variation in populations sculpt community behaviors? How will methods development for circadian research be used in disparate academic and commercial endeavors? These and other questions make it a very exciting time to be working as a chronobiologist.
Sightings of dwarf minke whales in the Southern Hemisphere during the SOWER cruises
(International Whaling Commission, 2024-04) Kato, Hidehiro; Matsuoka, Koji; Nakamura, Gen; Best, Peter B.
This paper examines sightings of dwarf minke whales during the SOWER cruises. A total of 12 sightings were made between 1994/95 and 2003/04, across a relatively wide latitude (37°S–62°S) but limited longitude, between IWC Management Area III (0–70°E) and V (130°E–170°W), with no sightings in Area I (0–60°W) or II (60°W–120°W). Despite this low number of sightings, most were close to the Antarctic Convergence at 58°S–65°S. There may be some seasonality in their southbound migration.
The SOWER programme in the Antarctic : background, aims and objectives
(International Whaling Commission, 2024-02) Best, Peter B.; Ohsumi, S.; Kato, H.; Donovan, G.P.
The International Whaling Commission (IWC) imposed limits on the catch of Antarctic minke whales close to the start of commercial whaling in the 1970s. These management efforts were hampered by the challenge of obtaining robust estimates of population size. Contemporary whale assessments largely relied on measuring changes in availability as a result of exploitation – usually catch per unit effort (CPUE). However, this approach was largely impractical for Antarctic minke whales due to: (a) the short time series of CPUE data; (b) the setting of relatively conservative catch limits, so that changes in CPUE due to exploitation were difficult to detect; and (c) the possibility that abundance had been increasing before this time due to over‐exploitation of other baleen whales. The IWC initiated a series of assessment cruises in 1978 designed to obtain abundance estimates for targeted management areas in the Antarctic. Designed by the IWC’s Scientific Committee, these cruises were independent of whaling operations. The vessels were chartered whale catchers provided by Japan for the duration of the programme – and by the Soviet Union for a period of seven years. With the eventual participation of 86 scientists from 16 IWC member states, this programme became a key part of the International Decade of Cetacean Research (IDCR), launched in 1975 as a response to the 1972 Stockholm Resolution that called for a 10‐year moratorium on commercial whaling and the intensification of research efforts. While originally planned as ‘Discovery’ marking and sighting cruises, the programme eventually relied almost exclusively on sighting methods. Lasting over 30 years and involving three circumnavigations of the Southern Ocean, it became one of the largest whale monitoring exercises ever undertaken.
Overview of the SOWER cruise circumpolar acoustic survey data and analyses of Antarctic blue whale calls
(International Whaling Commission, 2024-02) Shabangu, Fannie Welcome; Stafford, Kathleen M.; Findlay, Kenneth Pierce; Rankin, Shannon; Ljungblad, Don; Tsuda, Yasunari; Morse, Laura; Clark, Christopher W.; Kato, Hidehiro; Ensor, Paul
The International Whaling Commission (IWC) carried out blue whale research within its annual Southern Ocean Whale and Ecosystem Research (SOWER) cruises between 1996 and 2010. Over 700 sonobuoys were deployed to record blue whale vocalisations during 11 Antarctic and three low‐latitude blue whale cruises off Australia, Madagascar and Chile. The recorded acoustic files from Antarctic deployments were collated and reviewed to develop a database of digital acoustic files and the associated deployment station metadata of 7,486 acoustic files from 484 stations. Acoustic files were analysed using the automated detection template and visual verification method. We found a significant difference between the total number of acoustic recording hours (2,481) reported in the associated cruise reports and the currently available number of acoustic recording hours (1,541). Antarctic blue whale vocalisations (9,315 D‐calls and 24,902 Z‐calls) were detected on 4,183 out of the total 7,486 acoustic files. December had the lowest call rates; January and February yielded high call rates. While most sonobuoys (63%) were deployed between 1800hrs and 0600hrs, the majority of calls (62%) were detected during observation periods between 0600hrs and 1800hrs. The difference between the available and reported data is a significant concern. Reconciliation of these and any future IWC acoustic data is strongly recommended.
Water provisioning shapes carnivore community structure
(Elsevier, 2024-12) Somers, Michael J.; Walters, Michele; michael.somers@up.ac.za
Water provisioning is common in arid and semi-arid African ecosystems, but its effects on carnivore communities are not understood. Recently, Morin et al. documented the unexpectedly contrasting space-use patterns of dominant and subordinate carnivores around water sources, with dominant carnivores facilitating subordinate carnivores.
A field-friendly alternative to freeze-drying faeces for glucocorticoid metabolite quantification in animals of different feeding classes
(Elsevier, 2024-12) Osburn, Kayla Rae; Crossey, Bruce Gareth; Majelantle, Tshepiso L; Ganswindt, Andre
Monitoring stress-related faecal glucocorticoid metabolite (fGCM) concentrations is a reliable, popular and established approach for understanding wildlife responses to perceived stressors. To maintain fGCM integrity post-defaecation, faecal material must be promptly stored frozen, or dried to prevent continued suspected bacterial enzyme activity. We compare the effectiveness of freeze-drying with other field-friendly drying techniques (food dehydrator and homemade solar oven). We collected 10 fresh faecal samples each from nine species (giraffe, impala, blue wildebeest, plains zebra, African elephant, white rhino, cheetah, spotted hyena, and leopard) and monitored alterations in fGCM concentrations over time utilizing these different drying techniques. Our findings indicate that a homemade solar oven is as effective as freeze-drying faecal samples. A food dehydrator is also a suitable method for drying faecal samples for the carnivores monitored. Our findings provide field-friendly methods for researchers dealing with logistical constraints in remote field sites. • For all species examined, a homemade solar oven offers a practical and affordable alternative to freeze-drying faeces for fGCM quantification. • A food dehydrator provides an affordable alternative to freeze-drying faeces for fGCM analysis when monitoring carnivores. • Different faecal sample drying techniques should not be utilized within a single study to ensure comparable analyses of fGCM values.
First record of gastrointestinal parasites of African otters
(IUCN Otter Specialist Group, 2024-06) Somers, Michael J.; Loggenberg, Jancke L.; McIntyre, Trevor; michael.somers@up.ac.za
Parasites are found in many mammalian species, particularly in the gastrointestinal tract. They can spread from one species to another and cause severe diseases in some species. Parasite spread is especially important between wild and domestic animals because it can affect human health. In this study, the first record of gastrointestinal parasites in African otters is reported from South Africa. The two otter species investigated were the African clawless otter (Aonyx capensis) and the spotted-necked otter (Hydrictis maculicollis). We identified the parasite species in collected faeces and examined the differences in parasitic loads between the species and two distinct habitats. Scats were collected from latrine sites in two areas (a rural nature reserve and an urban park) and examined using Teleman’s concentration-sedimentation formalin/ether method. Parasites were identified up to the species level where possible, and loads were calculated. As we only found African clawless otter faeces in the natural area and spotted-necked otter faeces in the urban reserve, we could not determine if the results were caused by differences in habitat or inherent to the host species. Therefore, our results only provide the first record of parasites in these two species. The findings revealed that the parasite species varied between the two areas (or species), although there was no significant difference in parasite loads.

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