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Animals in urban areas can be exposed to human-mediated land use change and radiant heat (called urban heat island effect). Few studies have empirically evaluated the effects of urban heat on wild vertebrates. We live-trapped desert wild rodents from a large metropolitan area in the Sonoran Desert, USA, across seven field sites spanning three strata of land surface temperatures. During the summers of 2019 and 2020, we captured 116 adult pocket mice (Chaetodipus spp. and Perognathus spp.) and Merriam’s kangaroo rats (Dipodomys merriami) in mountainous urban parks and open spaces. We measured body condition, proxy for health, using percent body fat (i.e., fat mass divided by body mass). For mammals, this parameter estimates the storage of energy-rich fat, which is important for growth, survival, and reproduction. We measured body condition using a noninvasive quantitative magnetic resonance instrument. Site-level surface temperatures were measured using data loggers and long-term climate data. Results supported the prediction that body condition was greatest in cooler temperature strata compared to the hottest areas. To relate body condition to resource availability, we evaluated vegetation cover and degree of urbanization. Body fat of adult pocket mice was greater in areas with more vegetation cover and where nighttime temperatures and surface temperatures were lower and urbanization was greater. Kangaroo rats had more fat in areas with the lowest strata of surface temperature. These results demonstrate that extreme heat negatively covaries with small mammal body condition, which indicates that urbanization and climate change have the potential to reduce rodent fitness.

The Baja California peninsula is the second longest, most geographically isolated peninsula on Earth. Its physiography and the presence of many surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuring for a wide spectrum of organisms. Chaetodipus spinatus is endemic to the region and occurs on 12 associated islands, including 10 in the Gulf of California and two in the Pacific Ocean. This distribution makes it a model species for evaluating natural historical barriers. We test hypotheses associated with the relationship between the range of the species, patterns in other species, and its relationship to Pleistocene-Holocene climatic changes. We analyzed sequence data from mtDNA genes encoding cytochrome b (Cytb) and cytochrome c oxidase subunits I (COI) and III (COIII) in 26 populations including all 12 islands. The matrilineal genealogy, statistical parsimony network and Bayesian skyline plot indicated an origin of C. spinatus in the southern part of the peninsula. Our analyses detected several differences from the common pattern of peninsular animals: no mid-peninsula break exists, Isla Carmen hosts the most divergent population, the population on an ancient southern Midriff island does not differ from peninsular populations, and a mtDNA peninsular discordance occurs near Loreto.

Anthropogenic activities since the European colonization of the North American Great Plains have drastically altered landscape composition and configuration, subsequently affecting native biodiversity. These contemporary human-modified landscapes may affect mammal species’ distributions, diel activity patterns, habitat use, and interspecific interactions, though a better understanding of these effects on mammals occurring in remaining prairie landscapes is needed. To fill this gap, we surveyed 381 randomly selected sites in 2018, 2019, and 2020 using motion-sensing camera traps across the western part of the US state of Kansas (7,160,077 ha). Sites were separated by ≥2 km (x = 8.16 km, SD = 3.61), and cameras were secured to a metal post 40 cm above ground and randomly oriented toward the north or south. We placed an olfactory attractant (mixture of skunk essence and petroleum jelly) on a wooden stake 3 m in front of each camera. Cameras were in place at each site for 28 consecutive days for each year. We manually identified all mammal species detected at each site, collating these data into a database that included taxonomic information for 14 families of mammals (Antilocapridae, Bovidae, Canidae, Cervidae, Cricetidae, Dasypodidae, Didelphidae, Erethizontidae, Felidae, Heteromyidae, Leporidae, Mephitidae, Mustelidae, Procyonidae, Sciuridae, and Muridae) comprising 28 total species. We recorded 31,178 mammal photographs (nonindependent events) over 27,954 camera trap nights during 2018 (n = 10,351), 2019 (n = 9478), and 2020 (n = 8125). Additionally, we included the time and date of each photocapture. Moreover, we gathered survey-specific data useful for modeling species-specific detection along with site-level habitat composition data taken at each site each year. These data will be useful for examining habitat use, species distributions, diel activity patterns, and spatiotemporal interactions between species and across guilds of mammals occurring in a rapidly changing agro-prairie ecosystem. There are no copyright restrictions, but we ask researchers to cite this paper when using these data for publication.

Understanding the diet of an endangered species illuminates the animal's ecology, habitat requirements, and conservation needs. However, direct observation of diet can be difficult, particularly for small, nocturnal animals such as the Pacific pocket mouse (Heteromyidae: Perognathus longimembris pacificus). Very little is known of the dietary habits of this federally endangered rodent, hindering management and restoration efforts. We used a metabarcoding approach to identify source plants in fecal samples (N = 52) from the three remaining populations known. The internal transcribed spacers (ITS) of the nuclear ribosomal loci were sequenced following the Illumina MiSeq amplicon strategy and processed reads were mapped to reference databases. We evaluated a range of threshold mapping criteria and found the best-performing setting generally recovered two distinct mock communities in proportions similar to expectation. We tested our method on captive animals fed a known diet and recovered almost all plant sources, but found substantial heterogeneity among fecal pellets collected from the same individual at the same time. Observed richness did not increase with pooling of pellets from the same individual. In field-collected samples, we identified 4-14 plant genera in individual samples and 74 genera overall, but over 50 percent of reads mapped to just six species in five genera. We simulated the effects of sequencing error, variable read length, and chimera formation to infer taxon-specific rates of misassignment for the local flora, which were generally low with some exceptions. Richness at the species and genus levels did not reach a clear asymptote, suggesting that diet breadth remained underestimated in the current pool of samples. Large numbers of scat samples are therefore needed to make inferences about diet and resource selection in future studies of the Pacific pocket mouse. We conclude that our minimally invasive method is promising for determining herbivore diets given a library of sequences from local plants.

Chaetodipus nelsoni occurs on rocky substrates across the Mexican Altiplano. We investigated phylogeographic diversity within the species using morphologic, karyotypic, and molecular data. Data from nuclear (AFLP) and mitochondrial DNA support three distinct genetic groups with minimal substructuring coincident with biogeographic barriers previously identified in the Chihuahuan Desert and drainage basins of the Altiplano. We examined the morphological and karyotypic data in light of the molecular data. The results support recognition of three species within the currently accepted widespread C. nelsoni: 1) C. nelsoni restricted to a distribution centered on the El Salado River Basin; 2) elevation of C. n. collis to species, with two subspecies: one centered on Trans-Pecos Texas, the other on the Mapimí Basin (new subspecies); and 3) recognition of a new species, C. durangae, centered on the Nazas Basin and upper Río Mezquital drainage.

Abstract Morphological analyses are critical to quantify phenotypic variation, identify taxa, inform phylogenetic relationships, and shed light on evolutionary patterns. This work is particularly important in groups that display great morphological disparity. Such is the case in geomyoid rodents, a group that includes 2 of the most species-rich families of rodents in North America: the Geomyidae (pocket gophers) and the Heteromyidae (kangaroo rats, pocket mice, and their relatives). We assessed variation in skull morphology (including both shape and size) among geomyoids to test the hypothesis that there are statistically significant differences in skull measurements at the family, genus, and species levels. Our sample includes 886 specimens representing all geomyoid genera and 39 species. We used the geometric mean to compare size across taxa. We used 14 measurements of the cranium and lower jaw normalized for size to compare shape among and within taxa. Our results show that skull measurements enable the distinction of geomyoids at the family, genus, and species levels. There is a larger amount of size variation within Geomyidae than within Heteromyidae. Our phylomorphospace analysis shows that the skull shape of the common ancestor of all geomyoids was more similar to the common ancestor of heteromyids than that of geomyids. Geomyid skulls display negative allometry whereas heteromyid skulls display positive allometry. Within heteromyids, dipodomyines, and non-dipodomyines show significantly different allometric patterns. Future analyses including fossils will be necessary to test our evolutionary hypotheses.

Rodent ectoparasites are vectors for important pathogens of wildlife, domestic animals, and even zoonosis. Nevertheless, distribution patterns of ectoparasites are not fully understood; habitat, season, and host species are important predictors of distribution and prevalence. Heteromyid rodents are considered important reservoirs of diseases, given the presence of different ectoparasites and pathogens in them, and they offer the opportunity to learn about the ecology of parasites. The aim of the present work was to survey ectoparasites associated with heteromyid rodents near a National Protected Area in Chihuahua Mexico, south of the USA-Mexico border, and asses the effects of ecological factors (season, vegetation type, host species, and host body condition) on parasite infestation. We sampled five different locations from January 2018 to July 2022; 845 heteromyid rodents were examined and 49 fleas and 33 ticks were collected. Ectoparasites belonged to the Siphonaptera and Ixodida orders, including three families Ixodidae ( Riphicephalus sanguineus ), Pulicidae ( Pulex irritans ), and Ctenophthalmidae ( Meringins altipecten , M. dipodomys ). Five species of host rodents were captured, Dipodomys merriami , D. ordii , Chaetodipus eremicus , C. hispidus , and C. intermedius , but the last two species did not present any ectoparasites. Dipodomys merriami presented the highest flea and tick prevalence followed by D. ordii . We found parasitic partnerships between heteromyids according to ecological factors. The infestation in C. eremicus was related to body condition, vegetation type, and sex; in D. merriami , it was related to vegetation type and season, while D. ordii did not present a clear pattern of infestation. Our results suggest that the infestation patterns of heteromyid rodents in desert habitats are species dependent.

The factors influencing the distribution and abundance of ectoparasites in vertebrates have been thoroughly examined in rodents, particularly concerning ticks and fleas. However, there is a paucity of knowledge regarding mites. The aim of this study was to determine if host or landscape traits are responsible for the abundance of dermanyssoid and trombiculoid mites. Rodent captures were carried out in the northwest region of Mexico between 2018 and 2022 in order to collect mites of the superfamilies Dermanyssoidea and Trombiculoidea. We generated generalized linear models to determine if rodent characteristics or the Index of Relative Anthropization (IRA) contribute to the relative abundance of Dermanyssoidea and Trombiculoidea. The best generalized linear model for Dermanyssoidea suggests that mite abundance is influenced by the IRA and the terrestrial rodent abundance. There is a relationship between the abundance of terrestrial rodents and dermanyssoid mites. Data show that as anthropization increases, Dermanyssoidea abundance decreases. The model shows rodent abundance, and the IRA are key factors in Trombiculoidea abundance. Our findings indicate that trombiculoid mites increase alongside rodents but decline as the IRA increases. This is the first study to use an index to investigate the impact of relative anthropization on Dermanyssoidea and Trombiculoidea in Mexico.

Improving detection probabilities for rare species is critical when assessing presence or habitat associations. Our goal was to create a new small mammal trapping protocol that improved detection of rare species, such as the olive-backed pocket mouse (Perognathus fasciatus). We used three trap and bait types and trapped an area 4.4 times larger than the standard grid. We also assessed the effect of captures of non-target species on detection probability of pocket mice. Regardless of species, trap success was higher for Havaharts. We found that bait and trap type selection varied significantly by species, with pocket mice showing strongest selection for Havahart traps baited with bird seed. Increasing grid size, while maintaining a similar trapping effort, resulted in higher detection probability, although our analyses showed that effective grids can be about three-quarters of the size we use to achieve similar results. We were also able to demonstrate that by deploying a combination of different traps and baits it is possible to overcome the potential effect of non-target species (e.g., deer mice, Peromyscus maniculatus) on the detection probability of pocket mice. Our results show that simple changes to standard small-mammal trapping methods can dramatically increase the detectability of rare and elusive small mammals. Increasing detection probability of rare components of a community can improve the results and understanding of future studies.

A new species of Heligmostrongylus (Nematoda: Heligmonellidae) is described from the small rodents Ototylomys phyllotis (Cricetidae: Tylomyinae) and Heteromys gaumeri (Heteromyidae: Heteromyinae) in the Yucatan Peninsula, Mexico, based on studies of light and scanning electron microscopy, and partial sequences of COI, ITS1 and 28S rRNA. Heligmostrongylus yucatanensis n. sp. is characterized by a synlophe of 13 interrupted ridges (except those forming careen) in both sexes at midbody; males with a ventral cuticle inflation at anterior region of copulatory bursa, rays 9 and 10 long, comparable in length, and rays 9 strongly curved laterally at a right angle crossing ventrally rays 8; and females with a torsion of 180° to left of the posterior extremity. These characteristics were shared with Heligmostrongylus nematodes reported previously from O. phyllotis and Peromyscus yucatanicus (Cricetidae: Neotominae) also in the Yucatan Peninsula. The absence of intraspecific sequence variations in COI, and the low variation in D2-D3 expansion segments of 28S rRNA and ITS1 among the specimens obtained from the different hosts provided strong support that the worms found in the three rodent species belong to the same new species. The nine previously known species of Heligmostrongylus have been reported from caviomorph rodents of the families Cuniculidae, Dasyproctidae, Echimyidae, and Erethizontidae from the Neotropics. The occurrence of H. yucatanensis in three phylogenetically distant rodent species suggests that this nematode species could have the ability to expand its host range by colonizing new hosts.