Research Articles (Biodiversity and Conservation Biology)

Permanent URI for this collectionhttps://hdl.handle.net/10566/35

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Vocal repertoire and acoustic cues to individual identity in the Northern Rockhopper penguin (Eudyptes moseleyi)
(Taylor and Francis Ltd., 2026) Ludynia, Katrin; Turone, Vittoria; Zanoli, Anna
Northern Rockhopper penguins (Eudyptes moseleyi) are highly vocal seabirds. However, detailed descriptions of their vocal repertoire are currently unavailable. Here, we studied the vocal behaviour of this species and assessed the presence of acoustic cues of individuality across different vocal types. We collected audio and video recordings from an ex-situ colony at the Two Oceans Aquarium (Cape Town, South Africa) consisting of wild rescued individuals and their offspring. We combined the visual inspection of spectrograms with spectro-temporal acoustic analyses based on a source-filter theory approach. Our results showed that the vocal repertoire of the Northern Rockhopper penguin is made of three discrete vocal types: agonistic calls, uttered during agonistic interactions, contact calls, produced to maintain acoustic contact among group members when visually isolated, and ecstatic display songs, mediating territorial defence and mate attraction. Moreover, we demonstrated that all vocal types encode acoustic cues to the individual identity of the emitter. Studying the vocal repertoire of penguins is crucial for a deeper understanding of their social behaviour and may ultimately contribute to the conservation of this endangered seabird.
Concentration of chemical elements in dry mass of Pontederia crassipes Mart. for use as organic fertilizer in small-scale crops
(Universidad Autonoma Metropolitana, 2025) Naidoo, Sershen; Hernández-Fernández, Leslie; Carlos Lorenzo Feijoo, José
Background: the increasing demand and production costs of inorganic fertilizers motivate researchers to explore new ways to obtain organic fertilizers. Pontederia crassipes Mart., is an invasive aquatic plant that grows in a freshwater lagoon (La Turbina), in Ciego de Ávila, Cuba. It is extracted from the water and deposited on the shores of the lagoon, affecting the aesthetic value of the site. Objective: to determine the concentration of chemical elements in the dry mass of P. crassipes (in its floating and emerging growth condition), to recommend its possible use as organic fertilizer or mixed substrate in small area crops. Method: for the analysis of most of the chemical elements, both in the lagoon water and in the dry mass of P. crassipes, inductively coupled plasma optical emission spectrometry was used. Results: the water of a lagoon was characterized by high concentration of Ca. In the dry mass of P. crassipes (floating and emergent), Ca, N, and K had the highest concentrations (mg g-1), followed by Na and Al. Heavy metals had concentrations below the maximum permissible limits for organic fertilizers and substratum of the crop. The eight chemical elements quantified in the lagoon water (Ca, Cu, K, Mg, Na, P, S, and Zn) showed bioconcentration in P. crassipes (floating). Seven chemical elements showed translocation in P. crassipes (B, Ca, K, N, Na, and Sr). Conclusions: The dry mass of P. crassipes can be used as organic fertilizer or as a mixed substrate for small-scale crops. Floating P. crassipes can phytostabilize and phytoextract chemical elements in the La Turbina artificial freshwater lagoon.
A century later: discovery of a second Podospongia species offshore from the Table Mountain National Park MPA, South Africa
(Cambridge University Press, 2026) Samaai, Toufiek
A new sponge species (Demospongiae: Poecilosclerida: Podospongiidae) is described offshore from the Cape of Good Hope, on the southern edge of the Table Mountain National Park marine protected area. Podospongia capensis sp. nov. is compared to Podospongia natalensis, described by Kirkpatrick (1903) from the east coast of South Africa, as well as to all other Podospongia species described to date. The new species differs from P. natalensis in having a shorter, thicker stalk, lacking anisostrongyles as megascleres, and possessing a second category of large symmetrical aciculospinorhabds microcleres that are present in P. natalensis. Additionally, P. natalensis has larger oxeas and styles than those found in P. capensis sp. nov. Furthermore, the two species are geographically separated, with P. natalensis described from the Natal ecoregion, while P. capensis sp. nov. is described from the Southern Benguela ecoregion. The new species primarily differs from other congeners in external morphology and size of the oxeas and styles.
Heuweltjies as within-paddock indicators of veld condition in the Succulent Karoo: vegetation contrasts between mound and intermound habitats
(Elsevier B V, 2026) Samuels, Igshaan; Gallant, Luke; Inman, Emilia N.
Heuweltjies (microtopographic earthen mounds) are conspicuous across South Africa's semi-arid, winter-rainfall rangelands, yet their value as field-ready indicators of veld condition is under-tested. This study examines the suitability of heuweltjies as indicators of veld condition within paddocks in the semi-arid Succulent Karoo. We utilized a spatially explicit paired sampling design, comparing vegetation attributes on 16 mounds with adjacent intermound plots (the matrix), in the Ebenhaeser communal rangelands. We focused on operational diagnostics, which are repeatable, management-sensitive metrics derived from life-form balances, growth-form structure, and palatability-weighted abundance. Statistical comparisons utilized Generalized Estimating Equations (GEE) to ensure robust inference by accounting for the non-independence inherent in the paired plot design. Mound habitats consistently showed a strong utilization signal, characterized by significantly higher counts of palatable individuals, as well as high herb richness and Shannon diversity. This confirms the ecological function of heuweltjies as resource islands that concentrate desirable forage. Annual plants exhibited significantly higher abundance and cover on mounds, reflecting their sensitivity to the localized nutrient enrichment and disturbance inherent in these resource islands. Succulent shrubs (a key forage group) were significantly larger on mounds, yet grasses were more abundant on the intermound matrix, highlighting a competitive trade-off possibly driven by higher mound alkalinity or shrub competition. These results validate the inherent mound–intermound contrast as a robust, low-cost indicator framework. Formalizing metrics such as palatable plant count difference and annual proportion provides local managers with repeatable, management-relevant signals necessary for setting accurate utilization thresholds, thus improving the performance of broader veld condition assessments.
Revealing hidden diversity: new latrunculia and Iophon species porifera, demospongiae, poecilosclerida) from the continental shelf of the Namaqua ecoregion benguela ecosystem along with a range extension of latrunculia aciculatrunculia biformis
(Cambridge University Press, 2026) Samaai, Toufiek; Payne, Robyn Pauline; Kamwi, Blessing
Four new species of Poecilosclerida (Porifera, Demospongiae) assigned to the genera Latrunculia and Iophon are described from South Africa and Namibia, located in the Namaqua ecoregion. The Porifera occurring along the continental shelf within this ecoregion are relatively well-known, with 76 species formally described in previous literature. Of these, 35 species belong to the Order Poecilosclerida. Additionally, Latrunculia (Aciculatrunculia) biformis is reported from the continental shelf on the west coast of South Africa, extending its range further northwards into the South Atlantic. DNA barcoding and molecular phylogenetic analyses were employed to ensure accurate taxonomic assignment and designation of new species.
Habitat modification by grazing lawns reduces soil mite diversity in a South African National Park
(John Wiley and Sons Inc, 2026) Grootboom, Claire; Samuels, Igshaan; Engelbrecht, Adriaan
Soil mesofauna are an integral part of the functioning of an ecosystem. They are relatively small in body size, occur in varying habitats and operate in a range of ecological niches. Soil mites are quite sensitive to changes in their environment and contribute to several important ecosystem services in their environments. This investigation aimed to determine how soil mite communities change in and around lawns in the Bontebok National Park (BNP). Sites that were sampled were categorised into lawns, ecotones and natural vegetation. Soils were collected to analyse physio-chemical parameters and to evaluate species composition of soil dwelling mites. Shannon and Simpson indices were used to determine species diversity of the different zones sampled and soil properties were used to generate PCAs and boxplots. There were changes in mite populations and community structure that were noticed in and around grazing lawns in the park, with a great reduction in diversity in lawns and the highest diversity seen in the ecotones. Lawns had higher proportions of macro and micronutrients, in addition to higher heavy metal content, which affected the oribatid mite populations inhabiting those areas. The establishment of lawns in the BNP had a negative impact on the mite populations in the park. This can be a major concern to soil mite communities in the park as they act as a vital component of the ecosystem, and contribute importantly to the overall functioning of their environment.
Distribution and status of reptile species in south-eastern Zimbabwe
(Taylor and Francis Ltd., 2025) van Wyk, Kurt; Maritz, Bryan; Clegg, Bruce William
While the loss of biodiversity in response to anthropogenic drivers is well documented, reptiles are rarely prioritised in global conservation efforts. Although more than 20% of all reptile species are currently listed as threatened, and a growing body of evidence highlights the sensitivity of reptiles to habitat change, basic information on the distribution, natural history, and regional conservation status of African reptiles remains sparse. Habitat loss through agricultural land-use change is regarded as the primary threat to global biodiversity and to southern African reptiles in particular. Arid and semi-arid ecoregions in southern Africa have been identified as areas of global conservation priority for reptiles. However, the status of Zimbabwe’s reptiles remains largely unknown. Limited resources and more urgent concerns have hampered what Zimbabwe has been able to achieve with respect to international conservation initiatives. Furthermore, the ecological impacts of recent, wide-scale land-use change in the country have received little attention. As legacies of historical land-use change are acknowledged as determinants of current landscape ecology, addressing the long-term effects of land-use change on Zimbabwe’s reptiles is crucial for effective conservation and management. Here we provide a complete account of the reptile taxa recorded in south-eastern Zimbabwe. We discuss sources of spatial and temporal bias in the occurrence dataset and highlight the importance of the region’s protected area network for conserving reptile diversity. Our study increases the number of published reptile occurrence records from the region by an estimated 285%
Vulnerability of marine megafauna to global at-sea anthropogenic threats
(John Wiley and Sons Inc, 2026) Waller, Lauren; VanCompernolle, Michelle; Morris, Juliet
Marine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species’ vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at-sea threats. The threats we considered included individual fishing gear types, climate-change-related subthreats not previously assessed, and threats associated with coastal impacts and maritime disturbances. Our ratings resulted in 70 species having high vulnerability (v > 0.778 out of 1) to at least 1 threat, primarily drifting longlines, temperature extremes, or fixed gear. These 3 threats were also considered to have the most severe effects (i.e., steepest population declines). Overall, temperature extremes and plastics and other solid waste were rated as affecting the largest proportion of populations. Penguins, pinnipeds, and polar bears had the highest vulnerability to temperature extremes. Bony fishes had the highest vulnerability to drifting longlines and plastics and other solid waste; pelagic cetaceans to 4 maritime disturbance threats; elasmobranchs to 5 fishing threats; and flying birds to drifting longlines and 2 maritime disturbance threats. Sirenians and turtles had the highest vulnerability to at least one threat from all 4 categories. Despite not necessarily having severe effects for most taxonomic groups, temperature extremes were rated among the top threats for all taxa except bony fishes. The vulnerability scores we provide are an important first step in estimating the risk of threats to marine megafauna. Importantly, they help differentiate scope from severity, which is key to identifying threats that should be prioritized for mitigation.
Editorial expression of concern: PICSI vs. MACS for abnormal sperm DNA fragmentation ICSI cases: a prospective randomized trial
(Springer, 2025) Henkel, Ralf; Hasanen, Eman; Elqusi, Khaled
The Editor-in-Chief is issuing this Editorial Expression of Concern to alert readers that concerns have been raised about the data presented in this article. Specifically, Table 1 presents the demographic information about the PICSI arm of this study as a decimal percentage, even though such percentages are not possible for a cohort of 200. The authors have stated that the reason for this is that not all participants provide full information about all demographic characteristics, so in each case the values are a percentage of a number that is less than 200. However, the authors have not been able to provide patient-level data due to the confidentiality statement that was signed by participants included in this study, and so the Editor-in-Chief has not been able to confirm this explanation or to verify the number of participants who failed to return information for each demographic characteristic. Readers are advised to interpret the data presented in this article with caution
Identifying essential chemical descriptors for auxins, cytokinins, and gibberellins using principal component analysis
(Springer, 2025) Sershen Naidoo; Quintana‑Zaez Julio César; Gómez Daviel
Auxins, cytokinins, and gibberellins are plant growth regulators (PGRs) that significantly influence plant growth and development. Investigating their molecular descriptors is vital for understanding how these PGRs work in intricate networks, influencing each other’s activity and responding to environmental cues, but this can be challenging given that PGRs often mimic or interact with naturally occurring plant growth regulators, which are themselves a complex group of chemicals with diverse structures and functions. This motivated the present study, which evaluated the effectiveness of principal component analysis (PCA), a statistical method renowned for reducing the dimensionality of intricate datasets, in identifying the key molecular descriptors that distinguish these three plant growth regulators. A total of 212 molecular descriptors were previously determined. Using PCA, the study identified critical chemical descriptors for auxins, cytokinins, and gibberellins, including ring count, presence of secondary alcohols, and terminal primary C (sp2) structures. Importantly, the study also confirmed the value of PCA in identifying key molecular descriptors for PGRs in studies focused on understanding their mechanism(s) of action. This paper introduced a novel methodological approach that contributes meaningfully to the understanding of PGRs.
Evaluation of risks of oil contamination in endangered seabirds in Algoa Bay, South Africa, linked to ship-to-ship bunkering and anthropogenic maritime activities
(Elsevier Ltd, 2026) Ludynia, Katrin; Stassen, Monica; Fearon, Giles
This study evaluates the ecological risks of oil contamination to endangered seabirds in Algoa Bay, South Africa, linked to ship-to-ship (STS) bunkering activities and other anthropogenic maritime activities. Between 2016 and 2024, 378 oiled seabirds—primarily African penguins and Cape gannets—were admitted to rehabilitation centres, with over half linked to STS-related spills. An established modelling system was used to model the trajectory of oil from the MV Chrysanthi S spill in 2019 (400 L of Heavy Fuel Oil), using the simulated environmental conditions at the time of the spill. The model predicted that core foraging areas would have remained exposed to oil for about a week after the spill and that birds would have been found and rescued days after their contamination. Probabilistic modelling of 200 spill scenarios revealed high likelihoods of shoreline oiling and persistent surface contamination, especially during austral winter, when oil is more likely to reach Bird Island's seabird foraging areas. Spills from the offshore extent of anchorage area 2 are more likely to result in impacts on the seabird foraging areas. The model indicates that a high degree of conservatism is required when selecting ecological thresholds for impacts on African penguins, given the relatively high observed impacts despite low modelled surface thicknesses from a 400 L spill. These findings underscore the urgent need for stricter regulation of offshore bunkering in ecologically sensitive areas and improved preparedness for wildlife rescue and rehabilitation, especially in an area of such high biodiversity as Algoa Bay.
A place-based assessment of biodiversity intactness in sub-Saharan Africa
(Nature Research, 2025) Maritz, Bryan; Clements, Hayley S; Biggs, Reinette
Maintaining biodiversity is central to the sustainable development agenda1. However, a lack of context-specific biodiversity information at policy-relevant scales has posed major limitations to decision-makers2,3. To address this challenge, we undertook a comprehensive assessment of the biodiversity intactness of sub-Saharan Africa4 using place-based knowledge of 200 African biodiversity experts5. We estimate that the region has on average lost 24% of its pre-colonial and pre-industrial faunal and floral population abundances, ranging from losses of <20% for disturbance-adapted herbaceous plants to 80% for some large mammals. Rwanda and Nigeria are the least intact (<55%), whereas Namibia and Botswana are the most intact (>85%). Notably, most remaining organisms occur in unprotected, relatively untransformed rangelands and natural forests. Losses in biodiversity intactness in the worst-affected biomes are driven by land transformation into cropland in grasslands and fynbos (Mediterranean-type ecosystems), by non-agricultural degradation in forests and by a combination of the two drivers in savannas. This assessment provides decision-makers with multifaceted, contextually appropriate and policy-relevant information on the state of biodiversity in an understudied region of the world. Our approach could be used in other regions, including better-studied localities, to integrate contextual, place-based knowledge into multiscale assessments of biodiversity status and impacts.
Revealing hidden diversity: new Latrunculia and Iophon species (Porifera, Demospongiae, Poecilosclerida) from the continental shelf of the Namaqua ecoregion (Benguela ecosystem), along with a range extension of Latrunculia (Aciculatrunculia) biformis
(Cambridge University Press, 2026) Samaai, Toufiek; Payne, Robyn Pauline; Kamwi, Blessing
Four new species of Poecilosclerida (Porifera, Demospongiae) assigned to the genera Latrunculia and Iophon are described from South Africa and Namibia, located in the Namaqua ecoregion. The Porifera occurring along the continental shelf within this ecoregion are relatively well-known, with 76 species formally described in previous literature. Of these, 35 species belong to the Order Poecilosclerida. Additionally, Latrunculia (Aciculatrunculia) biformis is reported from the continental shelf on the west coast of South Africa, extending its range further northwards into the South Atlantic. DNA barcoding and molecular phylogenetic analyses were employed to ensure accurate taxonomic assignment and designation of new species.
The grazer Cymbula oculus (Patellogastropoda: Patellidae) serves as an important settlement substrate for several of its macroalgal prey
(National Inquiry Services Centre Ltd, 2025) Moosa, Waqeefah; Phillips, Jesse; Maneveldt, Gavin
Intertidal communities are predictably affected by both physical and biological factors, with herbivory as a particularly important factor. Instead of dense beds of macroalgae, which typically characterise the mid-eulittoral zone along the south coast of South Africa, at Kalk Bay this zone is dominated by a generalist grazer, the goat’s eye limpet Cymbula oculus. Despite its voracious grazing behaviour, this species of true limpet (family Patellidae) appears to positively influence macroalgal richness through epibiotic interactions. This study aimed to determine the role of C. oculus as an alternative settlement substrate for several macroalgal species that would otherwise be consumed by this grazer. Additionally, we wanted to determine whether the limpet’s density was on the increase, and, if so, what such an increase might mean for a future scenario at the site. Data collection and sampling took place within quadrats along transect lines. The quadrats were photographed to determine macroalgal cover on the limpet shells and on the surrounding primary rocky substrate, and analysed using ImageJ software. Additionally, C. oculus density was estimated, as well as macroalgal biomass on both the limpet shells and the primary rocky substrate. It was found that C. oculus shells are an important secondary substrate for macroalgae, and that species of foliose and turfy macroalgae benefit more than encrusting macroalgal species. The mean density of C. oculus, at 20 (SE 2.22) ind. m−2, was significantly greater than that reported two decades ago. The potential exists for increased cover abundance of chemically and morphologically defended macroalgae on the primary rocky substrate, a future scenario that seems increasingly possible given the increased C. oculus densities.
The influence of physicochemical variables on plant species richness and distribution in the coastal salt marshes of the Berg River Estuary, South Africa
(Elsevier B.V, 2025) Mngomezulu, Nomcebo T.; Rajkaran, Anusha; Veldkornet, Dimitri A.
The continuous distribution of coastal salt marsh habitats along an elevation gradient can be disrupted by tidal creeks running through them. Tidal creeks wind through salt marshes and create different environmental conditions for adjacent habitats. While studies have emphasized the importance of tidal creeks as links facilitating interactions in salt marshes, few have studied plant communities and physiochemical conditions associated with tidal creeks. This study determined the influence of creek physicochemical variables on the diversity and distribution of coastal salt marsh plants. Six transects in the lower reaches of the Berg River Estuary, South Africa were sampled over two seasons at sites with either the presence or absence of creeks. Species composition and abundance were analysed by replicate quadrats and paired with physicochemical variables (groundwater and sediment). The k-means of 20 species in 334 quadrats revealed four distinct clusters of salt marsh habitats, creeks, intertidal salt marsh, supratidal salt marsh and reeds. Species richness was higher along transects with creeks (16) compared to those with no creeks (5). The physiochemical variables, groundwater temperature, pH, dissolved oxygen, conductivity, and sediment variables (redox potential, organic content, percentage silt and percentage sand), significantly influenced the abundance of creek species. This study highlights the importance of tidal creeks in forming unique vegetation communities in salt marshes, where they act as refugia for intertidal species. It is suggested that tidal creek communities should be included in salt marsh vegetation descriptions and monitored in association with physicochemical variables in response to climate change.
Germination and establishment of Teramnus labialis (l.f.) sprenG plants are affected by scarification treatment used
(Sociedad Botanica de Mexico, A.C, 2025) Naidoo, Sershen; Acosta, Yanier; Sánchez, Jorge A.
Background: Some of the species that make up the legume family are used as animal feed and to improve soil fertility. However, their use is limited due to low seed availability and low germination rates. Questions: Which scarification treatment is most effective in increasing germination? What is the response of plants to growth under field conditions? Studied specie: Teramnus labialis (L.f.) Spreng. Study site and date: Ciego de Ávila, Cuba, 2019 year. Methods: Four scarification treatments (sanding, sulfuric acid, hot water, and liquid nitrogen (LN)) were evaluated under controlled laboratory and field conditions. Seed coat structures, imbibition capacity, electrolyte loss, and germination were studied under controlled laboratory conditions. Under field conditions, plant morphological traits were evaluated during the vegetative and reproductive phases. Results: Scarification with LN caused multiple cracks in the seed coat, while sulfuric acid caused wear and detachment of the seed coat. With the use of LN, seed imbibition and germination were improved. In addition, 78 % of plants emerged with this treatment and crop establishment was achieved 120 days after sowing. Conclusions: Scarification with LN of T. labialis seeds was the most effective treatment to improve germination and reduce the time to establishment of the species. © 2025 Sociedad Botanica de Mexico, A.C.
A decade of implementing the Biodiversity management plan for African penguins – successes, failures and lessons learnt
(Elsevier GmbH, 2025) Barham, Peter; Ludynia, Katta; Sherley, Richard; Waller, Lauren
The rapid decline of the African penguin Spheniscus demersus in the early 2000 s triggered the drafting of the first African Penguin Biodiversity Management Plan (BMP) published in 2013, to “halt the decline of the African penguin population”. Working Groups (WGs) were created with stakeholders involved in penguin conservation to facilitate the implementation of the BMP. This study reviews the execution of the plan (1) from aide memoires and reports circulated within these WGs between 2013 and 2022; (2) by interviewing (in 2023) some of the stakeholders involved to assess their perceptions of the BMP 10 years post-implementation; and (3) by assessing the effectiveness of some actions using available scientific data. Interviewees unanimously agreed that the plan improved the species's management and facilitated collaboration across institutions involved. Conservation actions identified as the most effective were 1) the rehabilitation of adults and chicks; 2) predator management and 3) habitat improvement with the provision of artificial nests. Scientific reviews of these actions validated their success. For example, rehabilitation effort may have increased the 2023 penguin breeding population by ca 7 %. Nevertheless, African penguin numbers continued decreasing and the species is now “Critically Endangered” on the IUCN Red List. Measures are still lacking in effectively increasing prey availability despite intensive engagement. Dedicated funding, trained capacity and accountability by relevant institutions undertaking their actions and deliverables were identified as essential for a more successful implementation of the BMP. Lessons learnt may pave the way for stronger conservation actions for African penguins and other threatened seabirds.
The first record of Cape Clawless Otters Aonyx capensis predating on African Penguins Spheniscus demersus
(Taylor and Francis Ltd, 2025) Ludynia, Katrin; Snyman, Albert; Purves, Arne
The African Penguin Spheniscus demersus, a critically endangered seabird endemic to southern Africa, faces substantial threats from terrestrial predators at its mainland colonies. Correct identification of the predator species is essential for effective conservation management. This study provides the first documented evidence of Cape Clawless Otter Aonyx capensis predation on African Penguins. We describe characteristic lesion patterns distinguishing otter predation from other predators, such as Caracal Caracal caracal. These findings underscore the importance of accurate predator identification to guide targeted mitigation strategies and highlight the need for adaptive management to protect vulnerable mainland African Penguin colonies from emerging predation pressures.
The agony of choice: comparing abundance estimates from multiple N-mixture model variants fitted to a reptile community dataset
(Society for the Study of Amphibians and Reptiles, 2025) van Wyk, Kurt; Maritz, Bryan
Ecological surveys rarely achieve perfect detection of target species, and failure to account for imperfect detection produces erroneous estimates of abundance. N-mixture models account for variation in detectability by separating the observation process from the ecological process that determines true site-level abundance, making these models theoretically well suited to studies of inconspicuous species, such as reptiles. Multiple N-mixture model variants have been published in different fields of ecology, but little is known about their ability to provide ecologically realistic abundance estimates from real-world observation data, especially for reptiles, which routinely have very low detection probabilities. Using a dataset of reptile observations from southeastern Zimbabwe, we compared estimates of five N-mixture model variants. For each species, we assessed the goodness-of-fit of each variant, proximity of each variant’s site-level abundance estimates to an ecologically realistic range of values, and congruence between these estimates. We were able to fit acceptable models only for the most frequently detected species in our dataset (9 of 25 species). We found that model fit varied significantly according to model variant as well as species occupancy and detection probability, and that model variant pairs were rarely congruent in their abundance estimates. Importantly, our results demonstrate that fitting a single N-mixture model variant to data sampled from an ecologically diverse community can yield artifactual variation in abundance estimates. Further case studies in reptile spatial ecology will help to identify circumstances in which a priori matching of species and method of abundance estimation may be possible. Until then, rigorous but adaptive survey design may be a more reliable means of avoiding bias than accounting for it statistically. We provide a framework for application of multiple N-mixture model variants in faunal ecology to guide analytical decision-making.
The impact of weather variation on the body condition of cape cobras (Naja nivea) in the Kalahari — implications for climate change
(Academic Press, 2025) Scholtz, Kim J.; Maritz, Robin A.; Maritz, Bryan
Hot and dry weather conditions are known to impact the body condition and the fitness of many organisms. However, this relationship has not been extensively studied in snakes. We examined the impact of variation in rainfall and temperature on body condition for a population of cape cobras (Naja nivea) at Tswalu Kalahari Reserve (Northern Cape Province, South Africa) over a period of five years during which time environmental conditions fluctuated substantially. We measured the mass and body length of 105 cobras, 58 from which we collected repeat measures, and calculated a body condition index (BCI) for each observation. We tested whether BCI was impacted by season, sex, and/or differences from expected mean monthly rainfall (during the preceding four-, 12-, and 24-week periods) and mean daily maximum temperature (during the preceding four-, 12-, and 24-week periods). Secondly, we tested whether BCI measures of cobras during the mating-season (September–November) were different between sexes and impacted by an index of environmental conditions (PC1 of rainfall and temperature) in the preceding summer. For our initial analysis, we found that the best-fitting model included season, sex, the relative amount of rain in the preceding twelve weeks (positive relationship), and the temperature in the preceding twelve weeks (negative relationship). Moreover, the BCI of cobras during the mating season was correlated with environmental conditions during the previous summer, with mating cobras exhibiting lower BCI measures following hot and dry summers. Our study reveals detrimental impacts of hot and dry conditions on cape cobra body condition, including measurable effects on body condition of mate-searching animals, following hot and dry summers. Taken together, we predict that prolonged hot dry periods, or increased frequency of hot dry periods in the future, might have detrimental effects on cape cobra populations in the Kalahari.

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