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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Territorial movements of African lions : can waterholes shape multiple central-place territories in a savannah ecosystem?
(Elsevier, 2025-06) Dejeante, Romain; Loveridge, Andrew J.; Macdonald, David W.; Madhlamoto, Daphine; Chamaillé-Jammes, Simon; Valeix, Marion
In territorial species, individuals need to regularly patrol their territory to display visual, auditory or olfactory signals or to detect the presence of intruders. Although territorial movements are often conceptualized as animals travelling along the boundaries of their territories (‘border-patrolling’ behaviour), the distribution of territorial cues could also match the distribution of resources when resources are spatially heterogeneous in their availability and found in stable patches, leading to the emergence of ‘multiple central-place territories’. Here, we explored how territoriality may shape the spatial behaviour of African lions, Panthera leo, in a savannah where waterholes are associated with aggregations of large herbivores throughout the year and are therefore well-known prey hotspots and key hunting sites for large carnivores. We hypothesized that male lions would be more likely to patrol a buffer area around the territory core to defend a core area where social interactions with groupmates occur, whereas female lions would more specifically patrol hunting sites, that is, waterhole areas. However, we found that both female and male lions repeatedly moved along straight paths between the waterholes located both in the core and in the periphery of their territories, potentially to defend multiple central-place territories driven by the distribution of waterholes in the landscape. These findings illustrate a case where territorial animals specifically mark feeding sites, increasing the renewal of territorial cues at these key places, potentially using long-distance territorial cues (that is, vocalizations) to mark uncovered areas, and thereby reducing the cost of patrolling large territories. Overall, multiple central-place territories provide new insights into how the spatial distribution of resources shapes space use in territorial animals.
Historical catch records of humpback whales and the assessment of early 20th century sea ice edge in climate models
(IOP Publishing, 2025-05) Vichi, Marcello; Seyboth, Elisa; Mazomba,Thando; Vermeulen, Els; Findlay, Ken; Meynecke, Jan-Olaf; De Bie, Jasper; Secchi, Eduardo; Dalla Rosa, Luciano; Roychoudhury, Alakendra
Assessment of historical environmental conditions in the Southern Ocean is limited by sparse oceanographic records prior to remote-sensing data. Whale catch data, particularly from humpback whales, can help fill this gap, as these whales inhabit waters near the sea ice edge. This study combines historical whale catch data with sea-ice model simulations from CMIP6 to assess the performance in the decade 1930–1939. The models were ranked based on their ability to simulate satellite-observed sea ice seasonality. The high-ranking models locate the sea-ice edge north of historical humpback whale catch regions, indicating higher sea-ice extent at the start of the 20th century, especially in November and December. It is recommended that models be tuned towards these early 20th century conditions while running the pre-industrial simulations. This interdisciplinary approach suggests that using only satellite-era data for model calibration may lead to overestimates of historical sea-ice extent, affecting future predictions.
Megagrazer loss drives complex landscape-scale biophysical cascades
(IOP Publishing, 2025-01) Hyvarinen, Olli; Te Beest, Mariska; Le Roux, Elizabeth; Kerley, Graham I.H.; Buitenwerf, Robert; Druce, Dave J.; Chen, Jiquan; Rapp, Linda; Fernandes, Joana; Cromsigt, Joris P.G.M.
Wild animals can modulate ecosystem-climate feedbacks, e.g. through impacts on vegetation and associated carbon dynamics. However, vegetation cover and composition also affect land surface albedo, which is an important component of the global energy budget. We currently know very little about the influence of wild animals on land surface albedo and the resulting climate forcing of these albedo changes. Leveraging a unique, ecosystem-scale, semi-experimental approach, we study how the local removals of the world's largest, terrestrial grazer, white rhinoceros (Ceratotherium simum), affected the coupling between fire dynamics, woody encroachment and surface albedo in Hluhluwe–iMfolozi Park (HiP), South Africa. Our path analysis revealed that areas in the park where more rhinos had been removed showed a stronger increase in burnt area and woody encroachment compared to areas with fewer rhinos removed, which were both related to a decrease in surface albedo. Increasing burnt area was further associated with higher rates of woody encroachment, indirectly reinforcing the negative effect of rhino loss on albedo. Our study demonstrates that removals of megagrazers in HiP were related to complex ecosystem-wide cascades with measurable impacts on land cover and surface albedo and consequences on climate forcing. This highlights the importance of restoring functional ecosystems by reinstating trophic processes.
High human presence is correlated with lower faecal glucocorticoid metabolite levels in an urban bird population
(Elsevier, 2025-04) Nhlapo, Kagiso B.; Cunningham, Susan J.; Sumasgutner, Petra; Ganswindt, Andre; McKechnie, Andrew E.; Ngcamphalala, Celiwe A.
Urban wildlife must cope with diverse challenges and stressors, including human presence. However, in addition to being a disturbance, humans can provide energy-rich food and protection from predators. We evaluated the impact of human presence on red-winged starlings (Onychognathus morio) in a highly urbanised environment using faecal glucocorticoid metabolite (fGCM) concentrations as a stress-related biomarker. We performed an adrenocorticotropic hormone (ACTH) challenge to validate a non-invasive method for quantifying glucocorticoids in red-winged starlings. Using this method, we quantified fGCMs in excreta collected from free-living starlings during weekdays (high human presence) and weekends (low human presence) to determine the birds' responses to fluctuating human numbers. Following the ACTH challenge, starlings' circulating glucocorticoid (GC) concentrations increased by 127 % within 30 min and the corresponding fGCM concentrations increased within 1 h of injection. Of the four enzyme immunoassays (EIA) tested, an 11-oxoaetiocholanolone EIA, performed best, detecting a 310 % increase in fGCM concentrations post-ACTH challenge and suggested a 1-h lag between injection and peak fGCM excretion in this species. Human foot-traffic was significantly higher on weekdays compared to weekends, yet free-living red-winged starlings showed overall 30.4 % lower fGCM concentrations on weekdays compared to weekends. Red-winged starlings consume a higher proportion of anthropogenic food on weekdays than weekends and we cannot rule out the possibility that diet-related alteration in gut passage time affect fGCM concentrations. However, the correlation between fGCMs and human foot traffic may also suggest urban red-winged starlings benefit from human presence. Our results raise the possibility that, under certain conditions, the benefits associated with human presence outweigh potential negative effects associated with human activity, at least during the non-breeding season.
The impact of the lunar cycle and season on small mammal communities near a large metropolitan area
(Wiley, 2025-05) Oosthuizen, Tasha; Oosthuizen, Maria Kathleen; Pillay, Neville
Small mammals are prey to a range of predators and consequently use environmental cues, such as light, to assess the level of predation risk in their environment. The lunar cycle significantly influences the fear landscape for prey species because their risk level varies with visibility. We conducted small mammal surveys in two communities in close proximity to each other on a peri-urban site in South Africa. We investigated the abundance, composition and diversity of these communities across the lunar cycle and seasons. As predicted, we trapped the highest number of individuals and species on new moon nights, which have low light levels and thus indicate a reduced perceived predation risk. Winter showed a higher abundance compared to the other seasons, which could be explained by a decline in naturally available resources in winter. We captured more individuals and species on one site compared to the other site, largely because of the different microhabitats in the two sites; one site had a lower density of trees and more bare soil areas. Our study provides the first evidence of the impact the lunar cycle has on small mammal communities in southern Africa. Based on our findings of decreased activity of small mammals under increased lunar visibility, we hypothesise that small mammal communities in southern Africa will be negatively affected by the increased occurrence of artificial light at night, which could have wider ecosystem impacts.
Birds with distinct ecological traits show varied haemoglobin adaptations along elevation gradients
(Wiley, 2025-04) Bhembe, Zamekile D.; Padidar, Sara; Bebbington, Kat; Kingma, Sjouke A.; Monadjem, Ara
Ecological systems are highly dynamic, with organisms continually adapting to various environmental stressors along natural gradients. Birds along elevation gradients serve as excellent models for examining physiological adaptations, such as elevated haemoglobin concentrations at high altitudes due to lower oxygen availability. This study aimed to examine how various ecological traits influence the haemoglobin concentration responses of multiple bird taxa to an elevation gradient. We measured haemoglobin concentration in 920 birds of 133 species at six sites representing an elevation gradient spanning from 60 to 1,600 m above sea level. Using MCMC Bayesian mixed models, we identified important ecological determinants of haemoglobin concentration and further ran separate models to test whether haemoglobin concentration responses to elevation differ between various functional groups of birds. Our results showed that haemoglobin concentration increased significantly with elevation and was strongly influenced by wing morphology, body mass, season, and primary lifestyle. The rate of increase with elevation varied by lifestyle: terrestrial and perching birds exhibited a steeper increase in haemoglobin concentration with elevation, while aerial birds also increased haemoglobin but at a more gradual rate. However, the remaining traits did not alter how species respond to hypoxia; for example, birds increased haemoglobin at the same rate in both the dry and wet seasons, meaning seasonal changes did not strongly impact elevation-driven haemoglobin adjustments. Elevation is the primary driver of variation, while lifestyle influences baseline levels rather than the rate of change. Despite differences in lifestyle-driven oxygen demands, birds exhibit a similar haemoglobin response to hypoxia at moderate elevations, where adjustments remain within physiological limits, indicating that hypoxia-driven haemoglobin adjustments occur independently of baseline oxygen demands. These findings demonstrate how birds regulate oxygen transport relative to ecological constraints, providing insights into their physiological flexibility across environmental gradients.
Linking climate variability to demography in cooperatively breeding meerkats
(Wiley, 2025-05) Thorley, Jack; Duncan, Chris; Manser, Marta B.; Clutton-Brock, Tim
Animal populations in arid environments, where extreme temperatures and erratic rainfall are normal, are particularly vulnerable to climate change. While numerous studies have examined the effects of temperature and rainfall on the breeding success and survival of arid-zone species, the mechanistic pathways linking climate variation to demography remain poorly described for most species. Using long-term data from meerkats (Suricata suricatta) in the Kalahari Desert, we show that increases in rainfall and primary productivity (as measured by normalized difference vegetation index) were associated with improved foraging success, daily body mass gain, and body condition, which in turn contributed to enhanced breeding success and survival. Conversely, high summer temperatures were associated with reduced foraging performance and body condition. Foraging efficiency declined when daily maximum summer temperatures exceeded 35°C, and at temperatures above 37°C, diurnal mass gains often failed to offset overnight mass losses. While high temperatures had short-term detrimental effects, runs of hot days were relatively infrequent and often coincided with periods of high primary productivity. As a result, individuals were rarely in poor condition during the hottest periods of the year, suggesting that they could recover any mass lost on hot days during subsequent cooler periods. Only when high temperatures persisted alongside low primary productivity did body condition drop sharply. Although temperature variation has not yet affected the demography of our meerkat population as strongly as rainfall variation, further warming in the region and the potential for more frequent and severe hot droughts are likely to have major implications for the species' distribution and persistence. Our study emphasizes the need to consider both rainfall and temperature variations across seasons, as well as their interactions, to better understand and predict the impacts of climate change on arid-zone animals. It also demonstrates the value of long-term, high-resolution behavioral and physiological data, including frequent, year-round weighing of animals, in establishing causal links between climate and demography.
Patterns and drivers of female extra-pair mating in wild Kalahari meerkats
(Oxford University Press, 2025-05) Herdtle, Annika; Duncan, Chris; Manser, Marta B.; Clutton-Brock, Tim H.
In many pair-living vertebrates, females commonly mate outside the pair bond, but when and why they do so is unclear. This behavior may stem from females seeking “good genes” or “compatible genes” from extra-pair mates superior to or less related than their partner. Variation in female ability to acquire extra-pair copulations, however, may also influence extra-pair paternity rates. We analyze 23 yr of parentage data to explore extra-pair paternity in wild Kalahari meerkats (Suricata suricatta), cooperative breeders where a single dominant pair monopolizes most reproduction in each group. When paired with a familiar breeding partner, females almost exclusively mate extra-pair to avoid inbreeding; however, even when paired with an unfamiliar male, extra-pair paternity still occurs. In our study of unfamiliar pairings, 14% of dominant female litters contained extra-pair paternity, with 90% of offspring sired by resident dominant males, 7% by extra-group males, and 3% by subordinate immigrant males. Results were not consistent with the compatible or good genes hypotheses: more closely related dominant pairs were not more prone to extra-group paternity; extra-group sires were not less related, heavier, or older than the resident dominant male; and offspring from extra-group matings did not demonstrate advantages over within-pair offspring. Extra-group paternity was more likely when dominant females were heavier, dominant males were lighter, more extra-group males visited, and few subordinate males resided in the group, suggesting extra-pair paternity rates are primarily driven by individual and social conditions. Whether females benefit from extra-pair paternity or simply mate with any available male remains unclear.
Inter-call intervals, but not call durations, adhere to Menzerath's law in the submissive vocal bouts of meerkats
(The Royal Society, 2024-12) Watson, Stuart Kyle; Zali, Mara; Falk, Nikola; Widmer, Paul; Manser, Marta B.
Diverse information encoding systems, including human language, the vocal and gestural systems of non-human animals and the structure of DNA and proteins, have been found to conform to ‘Menzerath’s Law’—a negative relationship between the number of units composing a sequence, and the size of those units. Here, we test for the presence of Menzerath’s Law in the vocal bouts produced in a submissive context by meerkats (Suricata suricatta). Using a suite of Bayesian mixed effects models, we examined 1676 vocal bouts produced by 89 wild meerkats, ranging from 1 to 590 calls in length, to determine whether the number of calls composing each bout had a negative relationship with the duration of those calls or their inter-call intervals. In contradiction to Menzerath’s Law, we found that the duration of vocalizations had a positive relationship with the number of calls in a bout. However, the duration of intervals between calls did have a negative relationship with bout size. Moreover, both calls and intervals had longer durations the closer they were positioned to the end of the bout. These findings highlight the multi-faceted ways in which efficiency trade-offs can occur in the vocal repertoires of non-human animals, shaping variability in the production of signal forms.
Size, scaling, and sexual size dimorphism in wild South African thick-tailed greater galagos (Otolemur crassicaudatus)
(Springer, 2024-12) Leigh, Steven R.; Sauther, Michelle L.; Cuozzo, Frank P.; Tordiffe, Adrian Stephen Wolferstan; Van Wyk, Ilana
The developmental bases of sexual size dimorphism vary across primates, with important implications for understanding the evolution of dimorphism. Here, we explore adult sexual size dimorphism and its developmental bases in Otolemur crassicaudatus. We aim to understand the anatomical pattern of adult sexual size dimorphisms and their developmental bases through allometric analyses of somatometrics. We caught and released wild subadult and adult animals annually at Lajuma Research Centre, South Africa from 2013 to 2023 (excepting 2020), and measured body mass and up to 23 body measurements. Among adults, males (mean body mass = 1242.89 g ± SD = 137.63 g, n = 91 observations of n = 52 individuals) are 1.21 times larger than females (mean body mass = 1027.55 g ± SD = 94.03 g, n = 85 observations of n = 44 individuals), possibly representing the highest body mass sexual dimorphism among extant strepsirrhines. The skeletal system shows limited sexual size dimorphism, suggesting decoupling of body mass size dimorphism and skeletal size dimorphism. Allometries lead to variation in adult sexual size dimorphism throughout the body, with high levels of dimorphism in circumferences, especially in the torso and proximal limb elements. Sexual selection, attributable to some level of intermale competition, probably accounts for sexual size dimorphism in this species. The conservatism of the skeletal system, combined with high body mass size dimorphism, may be related to generalized quadrupedalism and declining rates of leaping through ontogeny in the species. These findings complicate reconstructing and interpreting primate sexual size dimorphism in the fossil record.
Oxidative stress in the reproduction of mammals
(MDPI, 2025-03) Jacobs, Paul Juan; Bennett, Nigel Charles; pj.jacobs@up.ac.za
No abstract available.
Volatile odours reflect breeding status but not social group membership in captive Damaraland mole-rats
(Elsevier, 2025-04) Nichols, Hazel J.; Caspers, Barbara A.; Arbuckle, Kevin; Bennett, Nigel Charles; Hoffman, Joseph I.
In mammals, olfaction plays a key role in social behaviour, for example, in identifying mating opportunities and potential rivals. However, we still have a limited understanding of how social information is encoded in animal odours, including the social determinants of chemical similarity and diversity. Here, we used gas chromatography to analyse the chemical composition of swabs taken from the facial and anogenital regions of Damaraland mole-rats, Fukomys damarensis, a highly social subterranean mammal that relies almost exclusively on olfactory and tactile social cues. We found no sign of individual identity across the two body areas sampled; samples from the facial region and samples of the anogenital region from the same individual were not similar to each other, suggesting that these regions carry different information. However, chemical profiles varied significantly by sex and breeding status; female breeders differed from nonbreeders in their anogenital profiles and had higher chemical diversity in their facial profiles compared with both males and nonbreeders. Interestingly, we found no signals of social group identity. Instead, individual identity may be conveyed through signature mixes that are learned through frequent contact, rather than through specific odours associated with genetic kinship or social group membership. Our results highlight the complexity of chemical communication systems in social species and suggest that signals of group level identity are not necessary for behavioural responses based on group membership.
Local nutrient addition drives plant diversity losses but not biotic homogenization in global grasslands
(Nature Research, 2025-05) Chen, Qingqing; Blowes, Shane A.; Harpole, W. Stanley; Ladouceur, Emma; Borer, Elizabeth T.; Macdougall, Andrew S.; Martina, Jason P.; Bakker, Jonathan D.; Tognetti, Pedro M.; Seabloom, Eric W.; Daleo, Pedro; Power, Sally; Roscher, Christiane; Adler, Peter B.; Donohue, Ian; Wheeler, George; Stevens, Carly; Veen, G.F. Ciska; Risch, Anita C.; Wardle, Glenda M.; Hautier, Yann; Estrada, Catalina; Hersch-Green, Erika; Niu, Yujie; Peri, Pablo L.; Eskelinen, Anu; Gruner, Daniel S.; Venterink, Harry Olde; D’Antonio, Carla; Cadotte, Marc W.; Haider, Sylvia; Eisenhauer, Nico; Catford, Jane; Virtanen, Risto; Morgan, John W.; Tedder, Michelle; Bagchi, Sumanta; Caldeira, Maria C.; Bugalho, Miguel N.; Knops, Johannes M.H.; Dickman, Chris R.; Hagenah, Nicole; Jentsch, Anke; Macek, Petr; Osborne, Brooke B.; Laanisto, Lauri; Chase, Jonathan M.
Nutrient enrichment typically causes local plant diversity declines. A common but untested expectation is that nutrient enrichment also reduces variation in nutrient conditions among localities and selects for a smaller pool of species, causing greater diversity declines at larger than local scales and thus biotic homogenization. Here we apply a framework that links changes in species richness across scales to changes in the numbers of spatially restricted and widespread species for a standardized nutrient addition experiment across 72 grasslands on six continents. Overall, we find proportionally similar species loss at local and larger scales, suggesting similar declines of spatially restricted and widespread species, and no biotic homogenization after 4 years and up to 14 years of treatment. These patterns of diversity changes are generally consistent across species groups. Thus, nutrient enrichment poses threats to plant diversity, including for widespread species that are often critical for ecosystem functions.
Measuring urofecal glucocorticoid metabolites in broiler chicken : a noninvasive tool for assessing stress as a marker of welfare
(Elsevier, 2024-11) Wolf, Tanja Esther; Toppel, Kathrin; Jacobsen, Lea; Andersson, Robby; Touma, Chadi
The poultry industry is an important and still growing sector in many parts of the world. For ethical reasons and due to increased consumer awareness for animal welfare in production animals, it is of importance to establish a reliable and objective test system for monitoring and improving health and welfare. During the rearing process, broiler chickens are exposed to numerous potential stressors and management interventions (e.g. weighing of individual animals, preslaughter fasting and capture processes), but assessing the level of stress perceived by the animals entirely through behavioral observations can be challenging. Monitoring stress-related physiological markers, such as glucocorticoids, can be an accurate and presumably more objective addition. To avoid additional stressors induced by blood collection, a noninvasive approach using urofecal samples is advisable. However, a thorough validation is needed to establish a suitable test system for measuring stress hormone levels, including potential effects of the time of day of collection or the time that has elapsed since defecation. Therefore, the aim of this study was to test the stability of urofecal glucocorticoid metabolites (ufGCM) postdefecation, to determine time of day effects on ufGCM levels, and to investigate the effect of standard management procedures on ufGCM concentrations in broiler chickens. Our results revealed a time window of 4 h in which fecal samples from broilers can be collected without major alterations to the ufGCM concentrations. In this regard, a “fecal box” proved useful for collecting uncontaminated fresh samples. The time of day of sample collection did not influence ufGCM concentrations significantly. Moreover, the used assay proved to be sensitive enough to detect even small and short-lasting activations of the HPA axis induced by handling, confinement, and fasting. Thus, the system used can be a powerful and easy to apply tool in a chicken production setup for assessing stress as a marker of welfare in commercially housed broiler chickens, which in the long-term can also improve production, particularly with regard to process quality.
Garbage consumption by Arctic terrestrial predators in one of the most pristine land areas on Earth
(Norsk Polarinstitutt, 2024-01) Gort-Esteve, Araceli; Abrham, Muzit; Carøe, Christian; Masviken, Johannes; Freire, Susana; Lecomte, Nicolas; Pecnerova, Patricia; Angerbjorn, Anders; Filella, Jordi Bartolome; Noren, Karin; Dalerum, Fredrik
Garbage may cause substantial environmental perturbations, in part because of its consumption by wildlife. Such consumption may have direct health implications for animals and may also influence trophic relationships. Even in pristine Arctic ecosystems, wildlife feeding in marine environments consume garbage in the form of plastic debris transported by ocean currents. We show that Arctic wildlife in pristine terrestrial environments may also ingest garbage or food items derived from abandoned camp sites. We found the remains of a chocolate wrapper and a milk powder bag in two Arctic fox (Vulpes lagopus) scats and a piece of cloth in an Arctic wolf (Canis lupus arctos) scat collected near Nares Strait, northern Greenland, one of the most pristine terrestrial wilderness regions on Earth. Found on Washington Land and associated with long-abandoned camp sites, these three scats were among 657 Arctic fox scats and 92 wolf scats collected as part of a larger study. Our study demonstrates that these two highly opportunistic predators managed to consume garbage despite the almost complete lack of human activity in this High-Arctic region. Our results highlight that abandoned anthropogenic material in the High Arctic may function as a source of garbage for local terrestrial wildlife over extended time periods, and that garbage consumption may become a potential issue if human activity in remote Arctic regions increases.
Evaluating the use of marine subsidies by Arctic foxes without direct coastal access ; insights from stable isotopes
(Springer, 2024-09) Angerbjorn, Anders; Liden, Kerstin; Roth, James D.; Dalerum, Fredrik
The trophic structures of tundra ecosystems are often viewed as a result of local terrestrial primary productivity. However, other resources can be brought in through long-distant migrants or be directly accessible in coastal areas. Hence, trophic structures may deviate from predictions based on local terrestrial resources. The Arctic fox (Vulpes lagopus) is a small canid that may use marine resources when available. We used stable isotope values in Arctic fox fur and literature data on potential prey to evaluate Arctic fox summer resource use in a mountain tundra without coastal access. The dietary contribution of local prey, presumably mostly rodents, declined with declining rodent abundance, with a subsequent increased contribution of migratory prey relying on marine resources. Stable isotope values did not differ between this terrestrial area and an area with direct coastal access during years of high rodent abundance, but isotope values during low rodent abundances suggested less marine input than in a coastal population feeding primarily on marine prey. Our study shows that marine resources may be used by animals in areas without any coastal access, and we highlight that such partial coupling of ecosystems must be included in the modeling and assessments of tundra environments.
First record of ocular albinism in sub-Antarctic fur seal (Arctocephalus tropicalis) pups on Marion Island
(Springer, 2024-02) Shihlomule, Yinhla Desmond; Weideman, Eleanor A.; Van der Vyver, J.S. Fredrik; Conry, Danielle S.; Jordaan, Rowan Keith; De Bruyn, P.J. Nico
We report on an occurrence of ocular albinism in sub-Antarctic fur seal (Arctocephalus tropicalis) pups born on Marion Island, Prince Edward Archipelago. While previous observations have documented pups with atypical lanugo pelage colorations, this is the first case involving hypopigmentation of both fur and other tissues, including the eyes and nails. During the austral summer of 2021/22, we encountered four sub-Antarctic fur seal pups displaying this anomalous pigmentation. These anomalous individuals were found along two beaches on the island’s western side and one beach on the eastern side during an island-wide fur seal census. Although the characteristics observed strongly suggest ocular albinism, confirmation would be necessary through genetic analyses. The absence of melanin in mammalian eyes is known to compromise visual acuity, which may likely result in reduced survival beyond the weaning period, explaining the paucity of such adults in this well-observed population.
Forb diversity globally is harmed by nutrient enrichment but can be rescued by large mammalian herbivory
(Nature Research, 2025-03) Nelson, Rebecca A.; Sullivan, Lauren L.; Hersch-Green, Erika I.; Seabloom, Eric W.; Borer, Elizabeth T.; Tognetti, Pedro M.; Adler, Peter B.; Biederman, Lori; Bugalho, Miguel N.; Caldeira, Maria C.; Cancela, Juan P.; Carvalheiro, Luísa G.; Catford, Jane A.; Dickman, Chris R.; Dolezal, Aleksandra J.; Donohue, Ian; Ebeling, Anne; Eisenhauer, Nico; Elgersma, Kenneth J.; Eskelinen, Anu; Estrada, Catalina; Garbowski, Magda; Graff, Pamela; Gruner, Daniel S.; Hagenah, Nicole; Haider, Sylvia; Harpole, W. Stanley; Hautier, Yann; Jentsch, Anke; Johanson, Nicolina; Koerner, Sally E.; Lannes, Lucíola S.; Macdougall, Andrew S.; Martinson, Holly; Morgan, John W.; Olde Venterink, Harry; Orr, Devyn; Osborne, Brooke B.; Peri, Pablo L.; Power, Sally A.; Raynaud, Xavier; Risch, Anita C.; Shrestha, Mani; Smith, Nicholas G.; Stevens, Carly J.; Veen, G.F. Ciska; Virtanen, Risto; Wardle, Glenda M.; Wolf, Amelia A.; Young, Alyssa L.; Harrison, Susan P.
Forbs (“wildflowers”) are important contributors to grassland biodiversity but are vulnerable to environmental changes. In a factorial experiment at 94 sites on 6 continents, we test the global generality of several broad predictions: (1) Forb cover and richness decline under nutrient enrichment, particularly nitrogen enrichment. (2) Forb cover and richness increase under herbivory by large mammals. (3) Forb richness and cover are less affected by nutrient enrichment and herbivory in more arid climates, because water limitation reduces the impacts of competition with grasses. (4) Forb families will respond differently to nutrient enrichment and mammalian herbivory due to differences in nutrient requirements. We find strong evidence for the first, partial support for the second, no support for the third, and support for the fourth prediction. Our results underscore that anthropogenic nitrogen addition is a major threat to grassland forbs, but grazing under high herbivore intensity can offset these nutrient effects.
Interactive and unimodal relationships between plant biomass, abiotic factors, and plant diversity in global grasslands
(Nature Research, 2025-01) Spohn, Marie; Bagchi, Sumanta; Bakker, Jonathan D.; Borer, Elizabeth T.; Carbutt, Clinton; Catford, Jane A.; Dickman, Christopher R.; Eisenhauer, Nico; Eskelinen, Anu; Hagenah, Nicole; Hautier, Yann; Koerner, Sally E.; Komatsu, Kimberly J.; Laanisto, Lauri; Lekberg, Ylva; Martina, Jason P.; Martinson, Holly; Partel, Meelis; Peri, Pablo L.; Risch, Anita C.; Smith, Nicholas G.; Stevens, Carly; Veen, G.F. Ciska; Virtanen, Risto; Yahdjian, Laura; Young, Alyssa L.; Young, Hillary S.; Seabloom, Eric W.
Grasslands cover approximately a third of the Earth’s land surface and account for about a third of terrestrial carbon storage. Yet, we lack strong predictive models of grassland plant biomass, the primary source of carbon in grasslands. This lack of predictive ability may arise from the assumption of linear relationships between plant biomass and the environment and an underestimation of interactions of environmental variables. Using data from 116 grasslands on six continents, we show unimodal relationships between plant biomass and ecosystem characteristics, such as mean annual precipitation and soil nitrogen. Further, we found that soil nitrogen and plant diversity interacted in their relationships with plant biomass, such that plant diversity and biomass were positively related at low levels of nitrogen and negatively at elevated levels of nitrogen. Our results show that it is critical to account for the interactive and unimodal relationships between plant biomass and several environmental variables to accurately include plant biomass in global vegetation and carbon models.
Frequent failure of nutrients to increase plant biomass supports the need for precision fertilization in agriculture
(Nature Research, 2025-04) Carroll, Oliver H.; Seabloom, Eric W.; Borer, Elizabeth T.; Harpole, W. Stanley; Wilfahrt, Peter; Arnillas, Carlos A.; Bakker, Jonathan D.; Blumenthal, Dana M.; Boughton, Elizabeth; Bugalho, Miguel N.; Caldeira, Maria; Campbell, Malcolm M.; Catford, Jane; Chen, Qingqing; Dickman, Christopher R.; Donohue, Ian; DuPre, Mary Ellyn; Eskelinen, Anu; Estrada, Catalina; Fay, Philip A.; Fraser, Evan D.G.; Hagenah, Nicole; Hautier, Yann; Hersh-Green, Erika; Jonsdottir, Ingibjoerg S.; Kadoya, Taku; Komatsu, Kimberly; Lannes, Luciola; Liang, Maowei; Venterink, Harry Olde; Peri, Pablo; Power, Sally A.; Price, Jodi N.; Ren, Zhengwei; Risch, Anita C.; Sonnier, Gregory; Veen, G.F.; Virtanen, Risto; Wardle, Glenda M.; Waring, Elizabeth F.; Wheeler, George; Yahdjian, Laura; Macdougall, Andrew S.
Implementing precision fertilization to maximize crop yield while minimizing economic and environmental impacts has become critical for agriculture. Variability in biomass response to fertilization within fields, among regions, and over time creates simultaneous risks of under-yielding and overfertilization. We quantify factors determining fertilization responsiveness (i.e., biomass increases with fertilization) up to 15 years in 61 unfertilized rangelands on six continents. We demonstrate widespread multi-year variability in responsiveness, with fertilization increasing average yield by 43% but failing to improve biomass 26% of the time. All sites were responsive at least once, but only four of 61 responded in all plots and years. Modelled management scenarios highlighted that fertilizer cessation is likely to generate sizable economic savings but always reduces yield because of the difficulty in predicting when and where biomass will be unresponsive. This work reveals substantial scale-dependent variability in fertilization responsiveness globally, while clarifying the prospects and pitfalls of managing more spatially and temporally precise nutrient application.

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