Biology subjects

Hofer, H.

Publications and source records attributed to Hofer, H..

8 recordsLinked to original sources

bioRxiv2026

How do spotted hyaenas respond to decreased prey availability in their clan territories over the last decades?

Climate change can alter predator-prey dynamics by influencing the distribution and movements of migratory prey. Despite increasing research on predator-prey mismatches, how predators respond to changes in prey availability caused by climate change remains largely unknown, particularly for behaviourally flexible species such as central-place foragers. In the Serengeti National Park, Tanzania, increased rainfall in recent decades is thought to have altered the movement patterns of large herds of migratory herbivores, the main prey of spotted hyaenas (Crocuta crocuta) in the park, leading to a decrease in yearly migratory prey presence within hyaena clan territories. Between 1990 and 1994, migratory prey were present within hyena clan territories for about 12% of the year--mainly in May-June and November-December--dropping to just 7% between 2015 and 2019. Using longitudinal data from three Serengeti hyaena clans at the centre of the park monitored between 1990 and 2019, we investigated the impact of the observed decrease in migratory prey presence on the number of observations of hyaenas feeding at carcasses ("feeding events", n = 777), and explored associated changes in hyaena clan size. The vast majority of observed hyaena feeding events involved migratory prey species, with this relative proportion remaining constant throughout the study period. Annual patterns in the number of feeding events closely mirrored annual patterns of migratory prey presence in clan territories, with two distinct peaks mid-year and toward the end of the year. As migratory prey presence in the study clan territories declined over the years, the number of observed feeding events also decreased. However, the size of two out of three clans increased over time, suggesting that the decline in migratory prey presence in clan territories and in the number of observed feeding events did not negatively impact hyaena clans. This absence of decline in clan size may reflect the fact that hyaenas feed within their territories for only a small fraction of the year, although it also invites further investigation into the mechanisms hyaenas may employ to compensate for reduced prey availability and reduced feeding events within their clan territories.

ecology↗

bioRxiv2025

Compromised futures: gastrointestinal parasites reduce survival and recruitment but not reproductive performance in wild female spotted hyenas (Crocuta crocuta)

BackgroundGastrointestinal parasitic (GIP) infections can decrease the survival and reproductive performance of humans and livestock. Even so, the immediate and delayed fitness consequences of GIP in unmanaged wild mammal populations, particularly during the sensitive and energetically demanding early life stage, remain largely unknown. MethodsWe investigate non-invasively the effects of GIP during early life on the survival to adulthood, age at first reproduction and longevity of 68 individually known female spotted hyenas in the Serengeti National Park, Tanzania. We also test whether a high investment in gastrointestinal local immunity (i.e. faecal mucin and immunoglobulin A) and an elevated allostatic load (i.e. faecal glucocorticoid metabolites) decrease these measures of performance, when controlling for resource availability and maternal effects (i.e. maternal social rank) using logistic regression and Cox proportional hazards models. ResultsAncylostoma sp. infections and the level of immunoglobulin A both negatively associate with survival to adulthood, probably because of the damage caused by the parasite and resource allocation trade-off between immunity and maintenance. Conversely, maternal social rank has a positive influence on survival to adulthood and longevity. Immune responses, allostatic load and GIP do not affect the age at first reproduction, suggesting either no effect, a complex interaction between different life stages, or a more immediate time-dependent effect. ConclusionOur study highlights the critical role of GIP infections and maternal effects on early-life fitness and long-term outcomes in females of a wild carnivore, thereby contributing to our understanding of ecological dynamics in unmanaged ecosystems.

ecology↗

bioRxiv2025

Cytochrome c oxidase I deep amplicon sequencing for metabarcoding of equine strongyle communities: unexpectedly high Strongylus spp. burden in treated horses

Equines are parasitized by complex communities of Strongylidae (Nematoda) comprising multi-species infections. Currently, the Cyathostominae are most prevalent, while the Strongylus species are only rarely detected. Since eggs and, in most cases, infective larvae cannot be differentiated to species level, with the exception of Strongylus spp., species-specific knowledge of the pathology, epidemiology and ecology of these parasitic nematodes is limited. Reference sequence data for several cyathostomin species are limited or missing. Deep amplicon sequencing of internal transcribed spacer 2 (ITS-2) regions of nematodes has been used in equines previously, although barcoding studies demonstrate a better species resolution for the cytochrome c oxidase subunit I (COI) region. The present study introduces a nemabiome method based on the sequencing of COI fragments. This method was applied to compare third stage larvae, representing strongyle communities, derived from regularly treated (RT) and never treated (NT) equine populations from Brazil, France (only RT), Germany, Ukraine, the UK, and the USA. Samples were predominantly from horses, but some were obtained from Przewalskis horses (Ukraine), donkeys (Germany, Ukraine) and kulans (Ukraine). Most sequence reads (87.7%) were identified to the species level, but unclassified reads occurred more frequently in donkeys and kulans than horses. No obvious difference in species diversity and richness was observed between RT and NT equines. However, there were significant differences in species composition between the RT and NT groups. While Strongylus spp. were significantly more abundant in the NT groups, Cylicocyclus nassatus, Cylicostephanus longibursatus, and Cyathostomum catinatum were more abundant in the RT group, suggesting that strongyle communities in domestic equines may have been shaped by anthelmintic treatments in the last decades. The decreased classification success for reads from non-caballine equines suggests that there are more strongyle species specific for this rarely-investigated group and that additional efforts are needed to improve the sequence database, particularly for these hosts. Author summaryThis study shows that long-term deworming treatments have influenced strongyle nematode communities in equines. Our findings showed that regular deworming does not always reduce species richness and diversity. Noteworthy, we observed that the more pathogenic species such as Strongylus vulgaris and Strongylus edentatus were still present but in low abundance in equines. Due to their low abundance, less sensitive diagnostic methods, such as morphological examination of larval cultures might not detect these species, which would lead to an underestimated threat in equine herds. We applied an effective metabarcoding approach based on a reliable gene marker region to accurately detect these and other strongyle species in equines. The detection of various species was more effective for horse samples than for those from donkeys and kulans. An expansion of the current database that includes more specimens from more rare species obtained from different equine species can improve identification and understanding of these complex multi-species communities in the future. In summary, the study underscores the importance of continuing monitoring equine herds based on sensitive methods such as metabarcoding to evaluate the current nematode communities and to adapt and develop treatment strategies for managing strongyle infections in equines.

microbiology↗

bioRxiv2025

How monitoring behavior can inform conservation? The case of Spix's macaws under human care

The Spixs macaw (Cyanopsitta spixii), extinct in the wild since 2019, is currently maintained in exsitu breeding facilities. Captive breeding expanded the global population from 53 individuals in 2000 to ca. 400 by December 2025, enabling two soft releases. To support reintroduction, we introduce an ethogram of 85 behaviours and 1357 quantitative records based on observations of 123 birds at the ACTP Germany facility. Based on the analysis of the time-activity patterns of 10 pairs for 17 hours each, we also explore whether behavioural compatibility during the non-breeding season--measured here as time-activity similarity--relates to the breeding output of these pairs. Individual activity patterns were consistent, but females were markedly more synchronised with their mates than with other males. However, only pairs showing a high time-activity similarity bred successfully. Adjusting pair matching based on such similarity and improving general husbandry conditions (diet & enrichment) led to higher breeding output: pairs raising chicks increased from 0 in 2019 to 16 in 2024, fertility rates increased from 27% in 2019 to 64% in 2024, and annual chick output increased from 11 to 44 between 2019 and 2024. These results, based on 86 forced-mating attempts, support the idea that systematic behavioural monitoring can substantially contribute to enhancing conservation breeding in monogamous parrot species.

animal behavior and cognition↗

bioRxiv2024

Spotted hyena gut cross-talks:Symbionts modulate mucosal immunity

The intestinal mucosa is at the front line of host-microbiome interactions, but little is known about these interactions within natural populations. Here, we non-invasively investigated associations between the gut microbiome and mucosal immune measures while controlling for host, social, and ecological factors in 199 samples of 158 wild spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. We profiled the microbiome composition, including bacteria, fungi and parasites, using a multi-amplicon approach, and measured faecal immunoglobulin A and mucin. Probabilistic models indicated that both immune measures predict microbiome similarity among individuals in an age-dependent manner. The strength of the association effect varied, being strongest within bacteria, intermediate within parasites, and weakest within fungi communities. Machine learning regression accurately predicted both measures and identified the taxa driving these associations: symbiotic bacteria reported in humans and laboratory mice, unclassified bacteria, a hookworm, host DNA likely reflecting inflammation, and diet. Our findings indicate a complex interplay between the host, its environment and symbionts. These findings increase our knowledge of the gut microbiome in natural populations, which harbour highly dynamic and diverse eukaryotes under the influence of unpredictable environmental factors and where selection is not artificially biased.

ecology↗

bioRxiv2020

Keeping the kids at home can limit the persistence of contagious pathogens in social animals

In social species where offspring are reared together in communal burrows or similar structures, young animals typically do not engage in between-group contact during their development - a behavioural trait we call offspring with restricted between-group contact (ORC). The impact of this trait on the persistence of contagious pathogens that generate lifelong immunity in their hosts is currently unclear. We hypothesize that in populations with ORC, the formation, in groups, of a protective barrier of only recovered adults, prevents the transmission of this type of pathogens to the new susceptible hosts (i.e. young animals), thereby increasing the probability of epidemic fade-out. We implement a spatially implicit individual-based Susceptible-Infected-Recovered (SIR) model for a large range of host and pathogen traits and show that the epidemic fade-out probability is consistently higher in populations with ORC, especially when disease spread is fast (high basic reproduction number R0). We also show that ORC can counteract the cost of group-living in terms of disease risk to a greater extent than variation in other traits. We discuss our findings in relation to herd immunity and outline how they could be used to implement efficient management measures such as vaccinations.

ecology↗

bioRxiv2020

Effect of structural stability on endolysosomal degradation and T-cell reactivity of major shrimp allergen tropomyosin

BackgroundTropomyosins are highly conserved proteins, an attribute that forms the molecular basis for their IgE antibody cross-reactivity. Despite structural similarities, their allergenicity varies greatly between ingested and inhaled invertebrate sources. In this study, we investigated the relationship between the structural stability of different tropomyosins, their endolysosomal degradation patterns and T-cell reactivity. MethodsWe investigated the differences between four tropomyosins - the major shrimp allergen Pen m 1 and the minor allergens Der p 10 (dust mite), Bla g 7 (cockroach) and Ani s 3 (fish parasite) - in terms of IgE binding, structural stability, endolysosomal degradation and subsequent peptide generation, and T-cell cross-reactivity in a BALB/c murine model. ResultsDespite their conserved primary structure and consequent IgE co-reactivity, the invertebrate tropomyosins displayed different protein stabilities. Pen m 1 and Ani s 3, but not Der p 10 and Bla g 7 elicited differential melting temperatures that were pH-dependent. Endolysosomal experiments demonstrated differential degradation, as a function of stability, generating different peptide repertoires. Pen m 1 T-cell clones, with specificity for sequences highly conserved in all four tropomyosins, did not proliferate with Der p 10, Bla g 7 and Ani s 3, indicating that these peptides were not naturally produced for other invertebrate tropomyosins. ConclusionsOur data suggest that, although invertebrate tropomyosins exhibit a high degree of IgE cross-reactivity due to conserved B-cell epitopes, they do not necessarily share identical cross-reactive T-cell epitopes. This is likely due to differential endolysosomal processing as a function of different structural stabilities.

immunology↗

bioRxiv2019

Intravital multi-modal flux analysis reveals the transport mechanism of bile acids through hepatic microconduits

Small-molecule flux in tissue-microdomains is essential for organ function, but knowledge of this process is scant due to the lack of suitable methods. We developed two independent techniques that allow the quantification of advection (flow) and diffusion in individual bile canaliculi and in interlobular bile ducts of intact livers in living mice, namely Fluorescence Loss After Photoactivation (FLAP) and Intravital Arbitrary Region Image Correlation Spectroscopy (IVARICS). The results challenge the prevailing ‘mechano-osmotic’ theory of canalicular bile flow. After active transport across hepatocyte membranes bile acids are transported in the canaliculi primarily by diffusion. Only in the interlobular ducts, diffusion is augmented by regulatable advection. Photoactivation of fluorescein bis-(5-carboxymethoxy-2-nitrobenzyl)-ether (CMNB-caged fluorescein) in entire lobules demonstrated the establishment of diffusive gradients in the bile canalicular network and the sink function of interlobular ducts. In contrast to the bile canalicular network, vectorial transport was detected and quantified in the mesh of interlobular bile ducts. In conclusion, the liver consists of a diffusion dominated canalicular domain, where hepatocytes secrete small molecules and generate a concentration gradient and a flow-augmented ductular domain, where regulated water influx creates unidirectional advection that augments the diffusive flux.One Sentence Summary/Keywords Bile flux proceeds by diffusion in canaliculi, augmented by advection in ducts.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗