skip to main content

Search for: All records

Award ID contains: 1853934

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Abstract

    Toxoplasma gondiiis hypothesized to manipulate the behavior of warm-blooded hosts to promote trophic transmission into the parasite’s definitive feline hosts. A key prediction of this hypothesis is thatT. gondiiinfections of non-feline hosts are associated with costly behavior towardT. gondii’s definitive hosts; however, this effect has not been documented in any of the parasite’s diverse wild hosts during naturally occurring interactions with felines. Here, three decades of field observations reveal thatT. gondii-infected hyena cubs approach lions more closely than uninfected peers and have higher rates of lion mortality. We discuss these results in light of 1) the possibility that hyenamore »boldness represents an extended phenotype of the parasite, and 2) alternative scenarios in whichT. gondiihas not undergone selection to manipulate behavior in host hyenas. Both cases remain plausible and have important ramifications forT. gondii’s impacts on host behavior and fitness in the wild.

    « less
  2. Abstract

    The gut microbiota is critical for host function. Among mammals, host phylogenetic relatedness and diet are strong drivers of gut microbiota structure, but one factor may be more influential than the other. Here, we used 16S rRNA gene sequencing to determine the relative contributions of host phylogeny and host diet in structuring the gut microbiotas of 11 herbivore species from 5 families living sympatrically in southwest Kenya. Herbivore species were classified as grazers, browsers, or mixed-feeders and dietary data (% C4 grasses in diet) were compiled from previously published sources. We found that herbivore gut microbiotas were highly species-specific, andmore »that host taxonomy accounted for more variation in the gut microbiota (30%) than did host dietary guild (10%) or sample month (8%). Overall, similarity in the gut microbiota increased with host phylogenetic relatedness (r = 0.74) across the 11 species of herbivores, but among 7 closely related Bovid species, dietary %C4 grass values more strongly predicted gut microbiota structure (r = 0.64). Additionally, within bovids, host dietary guild explained more of the variation in the gut microbiota (17%) than did host species (12%). Lastly, while we found that the gut microbiotas of herbivores residing in southwest Kenya converge with those of distinct populations of conspecifics from central Kenya, fine-scale differences in the abundances of bacterial amplicon sequence variants (ASVs) between individuals from the two regions were also observed. Overall, our findings suggest that host phylogeny and taxonomy strongly structure the gut microbiota across broad host taxonomic scales, but these gut microbiotas can be further modified by host ecology (i.e., diet, geography), especially among closely related host species.

    « less
  3. Abstract

    Populations of large carnivores are declining in many parts of the world due to anthropogenic activity. Some species of large carnivores, however, are able to coexist with people by altering their behavior. Altered behaviors may be challenging to identify in large carnivores because these animals are typically cryptic, nocturnal, live at low densities, and because changes in their behavior may be subtle or emerge slowly over many years. We studied the effects of livestock presence on the movements of one large carnivore, the spotted hyena (Crocuta crocuta). We fit 22 adult female spotted hyenas with GPS collars to quantifymore »their movements in areas with and without livestock or herders present, in and around a protected area in southwestern Kenya. We investigated anthropogenic, social, and ecological effects on the speed of movement, distances traveled, long-distance movements, and extraterritorial excursions by spotted hyenas. Hyenas living primarily within the protected area, but in the presence of livestock and herders, moved faster, traveled over longer distances, and were more likely to be within their territories than did conspecifics living in areas without livestock and herders. Hyenas of low social rank were more likely than hyenas of high social rank to engage in long-distance travel events, and these were more likely to occur when prey were scarce. The movement patterns of this large African carnivore indicate a flexibility that may allow them to persist in landscapes that are becoming increasingly defined by people.

    « less
  4. Hopkins, Jack (Ed.)
    Abstract As fecal steroid methods increasingly are used by researchers to monitor the physiology of captive and wild populations, we need to expand our validation protocols to test the effects of procedural variation and to identify contamination by exogenous sources of steroid hormones. Mammalian carnivore feces often contain large amounts of hair from the prey they consume, which itself may contain high concentrations of hormones. In this study, we report first a validation of two steroid hormone antibodies, corticosterone and progesterone, to determine fecal concentrations of these hormones in wild spotted hyenas (Crocuta crocuta). Next, we expand on these standardmore »validation protocols to test two additional metrics: (i) whether hair from consumed prey or (ii) the specific drying method (oven incubation vs. lyophilization) affect steroid hormone concentrations in feces. In the first biological validation for the progesterone antibody in this species, progesterone concentrations met our expectations: (i) concentrations of plasma and fecal progesterone were lowest in immature females, higher in lactating females, and highest in pregnant females; (ii) across pregnant females, fecal progesterone concentrations were highest during late pregnancy; and (iii) among lactating females, fecal progesterone concentrations were highest after parturition. Our additional validation experiments indicated that contamination with prey hair and drying method are hormone-specific. Although prey hair did not release hormones into samples during storage or extraction for either hormone, its presence appeared to “dilute” progesterone (but not corticosterone) measures indirectly by increasing the dry weight of samples. In addition, fecal progesterone, but not corticosterone, values were lower for lyophilized than for incubated samples. Therefore, in addition to the standard analytical and biological validation steps, additional methodological variables need to be tested whenever we measure fecal hormone concentrations, particularly from predatory mammals.« less
    Free, publicly-accessible full text available January 27, 2023
  5. Free, publicly-accessible full text available January 1, 2023
  6. Free, publicly-accessible full text available November 1, 2022
  7. Free, publicly-accessible full text available September 1, 2022
  8. Grassland monitoring can be challenging because it is time-consuming and expensive to measure grass condition at large spatial scales. Remote sensing offers a time- and cost-effective method for mapping and monitoring grassland condition at both large spatial extents and fine temporal resolutions. Combinations of remotely sensed optical and radar imagery are particularly promising because together they can measure differences in moisture, structure, and reflectance among land cover types. We combined multi-date radar (PALSAR-2 and Sentinel-1) and optical (Sentinel-2) imagery with field data and visual interpretation of aerial imagery to classify land cover in the Masai Mara National Reserve, Kenya usingmore »machine learning (Random Forests). This study area comprises a diverse array of land cover types and changes over time due to seasonal changes in precipitation, seasonal movements of large herds of resident and migratory ungulates, fires, and livestock grazing. We classified twelve land cover types with user’s and producer’s accuracies ranging from 66%–100% and an overall accuracy of 86%. These methods were able to distinguish among short, medium, and tall grass cover at user’s accuracies of 83%, 82%, and 85%, respectively. By yielding a highly accurate, fine-resolution map that distinguishes among grasses of different heights, this work not only outlines a viable method for future grassland mapping efforts but also will help inform local management decisions and research in the Masai Mara National Reserve.« less
  9. ABSTRACT Host-associated microbial communities, henceforth ‘microbiota’, can affect the physiology and behavior of their hosts. In mammals, host ecological, social and environmental variables are associated with variation in microbial communities. Within individuals in a given mammalian species, the microbiota also partitions by body site. Here, we build on this work and sequence the bacterial 16S rRNA gene to profile the microbiota at six distinct body sites (ear, nasal and oral cavities, prepuce, rectum and anal scent gland) in a population of wild spotted hyenas (Crocuta crocuta), which are highly social, large African carnivores. We inquired whether microbiota at these bodymore »sites vary with host sex or social rank among juvenile hyenas, and whether they differ between juvenile females and adult females. We found that the scent gland microbiota differed between juvenile males and juvenile females, whereas the prepuce and rectal microbiota differed between adult females and juvenile females. Social rank, however, was not a significant predictor of microbiota profiles. Additionally, the microbiota varied considerably among the six sampled body sites and exhibited strong specificity among individual hyenas. Thus, our findings suggest that site-specific niche selection is a primary driver of microbiota structure in mammals, but endogenous host factors may also be influential.« less
  10. Farine, Damien (Ed.)