Rodentia Research Articles

Diversity, evenness, & richness of wild mammals along the Sutlej River, Punjab, Pakistan

Field surveys were conducted at three different water heads—Sulemanki, Islam, and Panjnad—of the Sutlej River from June 2021 to November 2021. This study aimed to estimate the diversity and assess the current threats to the mammalian fauna of the Sutlej River. During the surveys, a total of 266 individuals belonging to four orders, seven families, and twelve different species were observed. The greatest number of individuals belonged to the Rodentia order and the Muridae family. While the lowest number of individuals belonged to the Lagomorpha order and the Leporidae family, both had the same number of individuals. The Panjnad waterhead had the greatest diversity and evenness. The richness of mammals was the same at all three localities. Several threats, such as pollution, habitat destruction, and human−wildlife conflict, which drastically affect mammalian diversity, were observed throughout the investigation.

The Patterns and Reason for Chronographic Variability of Morphological Traits in Some Mammalian Species: Orders Rodentia and Carnivora

The Patterns and Reason for Chronographic Variability of Morphological Traits in Some Mammalian Species: Orders Rodentia and Carnivora

First report of Trypanosoma microti in Cricetid rodents from Querétaro, Mexico: Expanding the known distribution of Herpetosoma in the Mexican transition zone

Members of the subgenus Herpetosoma are specialized parasites of mammals of the order Lagomorpha and Rodentia. It is estimated that around 50 species within this subgenus are transmitted by several flea species. These parasites have recently gained attention from a public health perspective because several species have been reported to infect humans. Several species of the Herpetosoma subgenus have been recognized on the American continent, although there have been no reports from the Mexican Transition Zone. Therefore, the present study aimed to report the presence of a member of the Herpetosoma subgenus in cricetid rodents from Querétaro, Mexico.A total of 17 rodents belonging to three species, Peromyscus boylii, Peromyscus gratus, and Peromyscus melanophrys, were collected. Genetic material was extracted using the Chelex 100 resin, followed by PCR and sequencing of a fragment of 800 bp of the 18S ribosomal gene of the genus Trypanosoma. Out of these hosts, eight individuals of P. gratus (1♀), P. melanophrys (1♂), and P. boylii (3♂, 3♀) tested positive for Trypanosoma microti DNA, previously detected in the England and Japan. The present study, therefore, provides the first discovery of T. microti in Mexico, thereby increasing the known richness of species of the genus Trypanosoma in rodents from this country and the Mexican Transition Zone.

Geographic variability of carbon and nitrogen isotope ratios of nonvolant terrestrial small mammals (Rodentia) across 3 Brazilian biomes

Abstract In this study, we investigated landscape variability of the carbon and nitrogen isotopic composition of nonvolant small mammals in the 3 main Brazilian biomes (Amazon, Atlantic Forest, and Cerrado) while also considering the differential spatial distribution of C4 plants in these biomes. We compiled a subset of data on stable carbon and nitrogen isotope ratios from nonvolant small mammals of the order Rodentia and compared the aggregated isotopic variability at the biome level using classical δ13C–δ15N biplot. The concept of isotopic niche width was used to test whether different foraging attributes drive their isotopic composition, while a Bayesian isotopic mixing model was used to estimate the proportion of 3 main food categories available to these small mammals. We also developed isoscapes in the Brazilian biomes, interpolating animals δ13C and δ15N based on the geographic coordinates of each sample and “sourcescapes” considering geographic variation of the dietary sources. The findings of this study advance our understanding of the foraging ecology of small mammals in biodiversity-rich regions of the Neotropics. Classical methodologies such as stomach content confirmed dietary choices revealed by the stable isotopic composition and also highlighted the importance of C3 and C4 plants in the diet of this group of animals, especially in biomes such as the Atlantic Forest and Cerrado, where there is a predominance of highly altered landscapes. These results confirm that replacing the original vegetation with C4 crops has altered the feeding patterns of small mammals, which could lead to critical ecological changes in the trophic structure of these areas. Vertical stratification of the dietary niche and the interaction between biome and foraging lifestyle were also observed. However, in each biome, there was significant intraspecific and interspecific variation caused by preferences for ingestion of plant and animal material, leading to different degrees of omnivory. Finally, the high local variability between individuals and species requires a larger sampling design that may also contribute to improved spatial resolution of the isoscapes.

Rodents of Bahir Dar Blue Nile River Millennium Park, Ethiopia.

Rodents are mammals of the order Rodentia, which are found in all continents except Antarctica. They are the most diverse groups of mammals representing 41% of all mammals and they are known with 33 families, 481 genera, and about 2277 species. The present study was conducted from December 2018 to August 2019 both during the dry and wet seasons using Sherman traps and live traps. Four trap sites namely forest, bushland, grassland, and sugarcane plantation were selected for data collection. Shannon-Wiener diversity index (H') was used to compute rodent species diversity, Simpson's index (D) to assess the number and abundance of rodents in the different habitats, and one-way ANOVA and independent samples t-test were used for data analysis. A total of 163 individual rodents were captured in 1776 trap nights of which 125 individuals were captured using live traps in 1176 trap nights and 38 individuals using snap traps in 600 trap nights. Among the total individual rodents captured in the Bahir Dar Blue Nile River Millennium Park, 63.8% (n = 104) were males and 36.2% (n = 59) were females. Males outnumbered females in all the grids and the difference was significant (t = 31.5, df = 10, p < 0.05). The relative abundance of rodent species indicated that 42.4% (n = 53) were Arvicanthis niloticus, 26.4% (n = 33) Rattus rattus, 17.6% (n = 22) Mus musculus, 8% (n = 10) Mastomys natalensis, and 5.6% (n = 7) Arvicanthis abyssinicus. There are more individual specimens of A. niloticus than other species identified in the area (F = 698.22, df = 4, p < 0.05). Distribution of rodents varied among the different habitats. As a result, the bushland habitat showed more diversity of rodents (H = 0.98) and comprised relatively the highest (51.2%, n = 64) number of individuals captured, while the forest habitat supported the lowest number of rodents (4%, n = 5), and the difference showed a significant difference (F = 873.37, df = 3, p < 0.05). Population density with 95% confident interval estimated as 166 individuals/ha (95% CI:164.43-167.57). The present study provides basic information about population dynamics of rodents and contributes to design conservation strategies for rodents in particular and other biota of the area in general.

Is the general threatened status of four mammal groups affected by taxonomic changes over time?

The geographic range is a critical factor in assessing species’ threatened status on the IUCN Red List. A smaller geographic range increases the likelihood of a species being classified as threatened. Taxonomic revisions, which can split a widely distributed taxon into multiple smaller-range species, may elevate the threatened status for these newly recognized species. While taxonomic splitting is thought to increase the perceived threatened status of species, data on birds suggest the opposite, with newly recognized species being less threatened. No similar analysis has been conducted for mammals until now. This study compares the relationship between the number of recognized and threatened species in four mammalian orders (Carnivora, Cetartiodactyla, Chiroptera, and Rodentia) between 2005 and 2022. It was found that increases in species numbers due to taxonomic revisions correlated with increases in threatened species, particularly in Primates and Cetartiodactyla. The overall threatened status of these groups changed over time, with Primates and Cetartiodactyla becoming more threatened, while Rodentia became less threatened. We emphasize the need for consistent criteria in IUCN assessments to avoid biases, and we recommend that changes in the threatened status should only occur with robust evidence.

Investigating cryopreservation techniques for maintaining morphology and in vitro viability of cartilage and skin from Spix's yellow-toothed cavies (Galea spixii Wagler, 1831) for conservation through biobanks.

Conservation of the genetic diversity through skin and cartilage biobanks represents an essential strategy for maintaining biodiversity. Biobanks for the wild species of the order Rodentia have been little studied. Considering that the cryopreservation technique has specific relationships with the tissue and species of interest, we propose investigating different techniques for preserving tissue integrity and cell viability after cartilage and skin culture from Spix's yellow-toothed cavies. Subsequently, two techniques [solid-surface vitrification (SSV) vs. slow freezing (SF)] were used for cartilage and skin cryopreservation. Tissues not subjected to cryopreservation were used as controls. All tissues were evaluated for morphology and proliferation by histological techniques. Moreover, fragments were cultured, and cells were evaluated for viability, proliferation, metabolism, and apoptosis. Regardless of the cryopreservation technique, no differences were observed for the thickness of the epidermis, dermis, skin, spinous and basal layers, fibroblasts, and proliferative activity regarding the number of nucleolar organizer regions (NOR). SSV ensured better maintenance of epidermal cells, normal chondrocytes, filled gaps, collagen fibers, proliferative activity by NOR area/cell, and reduced perinuclear halos and empty gaps compared to SF. SF ensured the conservation of corneum thickness compared to the control. Although both techniques promoted cell recovery after culture, cells from SF resulted in better subconfluence time and day with cell growth around fragments compared to SSV. In conclusion, both cryopreservation techniques resulted in viable cells after culture. However, SSV promoted better maintenance of tissue morphological integrity, and SF ensured the preservation of all cell quality parameters in Spix's yellow-toothed cavies.

First report of a leucistic Brown Agouti (Dasyprocta variegata) in Bolivia

Abstract Cases of anomalous coloration are regularly reported in Neotropical mammals, including the rodent family Dasyproctidae (agoutis and acouchis) where leucistic and albino individuals have been observed. Here, we document the first case of leucism in the Brown Agouti (Dasyprocta variegata) in Bolivia. During a camera trap survey of the Barba Azul Nature Reserve, we obtained footage of a Brown Agouti with a completely white body. Additional pictures of this individual revealed that it has black eyes, indicating leucism instead of albinism. Previous observations (since 2017) of a white agouti in the area suggest that these anomalously colored individuals can survive in the wild. Rare observations of top predators suggest a relatively low predation pressure in the area. We had only one record of a South-American Puma (Puma concolor) during our camera trap survey. Hence, leucistic individuals of a common prey species might also be indicative of the dwindling population densities of top predators in the region.

The Distribution and Host-Association of the Vector Chigger Species Leptotrombidium imphalum in Southwest China.

Leptotrombidium imphalum is a species of chigger mites, and it can serve as a transmitting vector of scrub typhus. Southwest China is an important focus of scrub typhus. Based on the field investigation in southwest China from 2001 to 2022, this article presents the first report on the distribution and infestation of L. imphalum on rodents and other sympatric small mammals in the region. A total of 2161 L. imphalum were identified from 218 small mammal hosts in 21 of 114 survey sites. The 17 host species of L. imphalum crossed 13 genera and 5 families in 3 orders (Rodentia, Eulipotyphla, and Scandentia), indicating the low host specificity of the mite. The Asian house rat (Rattus tanezumi) was the dominant host species in the 21 sites where L. imphalum were collected, and 49.38% of mites were found on R. tanezumi. Different small mammals had different susceptibility to the infestation of L. imphalum. The prevalence (PM = 27.66%), infestation mean abundance (MA = 6 mites/per examined host), and mean intensity (MI = 21.69 mites/per infested host) for L. imphalum on the shrew gymnure (Neotetracus sinensis) were much higher than those on other host species (p < 0.05), indicating N. sinensis had a high susceptibility to the infestation of L. imphalum. The infestation indices for L. imphalum on small mammal hosts varied along different altitude and latitude gradients (p < 0.05), indicating the environmental heterogeneity of the mite infestation. Leptotrombidium imphalum exhibited an aggregated distribution among different individuals of its hosts. Besides the low host specificity of L. imphalum, the prevalence of the mite was positively correlated with the occurrence of scrub typhus, indicating the potential risk of the mite.

Trophic diet of the Long-eared owl Asio otus (Linnaeus, 1758) (Aves, Strigidae) in the Daya d'El-Gouffa (Laghouat, Algeria)

This research aims to study the trophic diet ofthe long-eared owl Asiootus and based on the examination of 120 regurgitation pellets of this raptor. These pellets were collected during the period from August to november 2020, near the Dayad'El-Gouffa located in the region of Laghouat. The analysis of the 120 pellets revealed a total of 273 individuals divided into 39 species belonging to four zoological classes. The consumption of small mammals, mainly Rodentia-Gerbillidae, is very common in arid environments. These constitute the basis of the diet of this raptor. Of the four families of rodents consumed, the Gerbillidae family is the most dominant one. It clearly stands out from the other families with a very high rate of 92.5% of the total rodents consumed. The Dipodidae are the least consumed (4.8%). In terms of species, Pachyuromusduprasi is the most dominant species with 31.5%. The values of the Shannon-Weaver index seem to be high. The highest one is recorded in november with 4.2 bits against 3.1 bits recorded in august. The calculated equitability values tend towards one for all four months of the study, so the numbers of the different components of the long-eared owl diet tend to be in balance with one another. This implies that Asiootus behaves as a generalist opportunistic predator.

Testicular histomorphometric patterns and spermatogenesis dynamics of Oecomys bicolor tomes, 1860 (Rodentia: Cricetidae).

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour.

Presence of Trypanosoma cruzi TcI and Trypanosoma dionisii in sylvatic bats from Yucatan, Mexico.

Chagas disease is caused by Trypanosoma cruzi, whose genetic structure is divided into six discrete typing units (DTUs) known as TcI-TcVI. In the Yucatan Peninsula, Mexico, information regarding the DTUs circulating in wild mammals is scarce, while this is important knowledge for our understanding of T. cruzi transmission dynamics. In the current study, we sampled wild mammals in a sylvatic site of the Yucatan Peninsula and assessed their infection with T. cruzi by PCR. Then, for infected mammals, we amplified and sequenced nuclear and mitochondrial T. cruzi genetic markers for DTU identification. In total, we captured 99 mammals belonging to the orders Chiroptera, Rodentia and Didelphimorphia. The prevalence of infection with T. cruzi was 9% (9/99; 95% CI [5, 16]), and we identified TcI in a Jamaican fruit bat, Artibeus jamaicensis. Moreover, we fortuitously identified Trypanosoma dionisii in another Jamaican fruit bat and detected an unidentified Trypanosoma species in a third specimen. While the latter discoveries were not expected because we used primers designed for T. cruzi, this study is the first to report the identification of T. dionisii in a bat from Yucatan, Mexico, adding to a recent first report of T. dionisii in bats from Veracruz, and first report of this Trypanosoma species in Mexico. Further research is needed to enhance our knowledge of T. cruzi DTUs and Trypanosoma diversity circulating in wildlife in Southeastern Mexico.

The Evolution of Rodent Tail Morphology.

AbstractPopulation-level variation in rodent tail structures has been variously attributed to facilitating social communication, locomotion, thermoregulation, and predator avoidance. Little is known, however, about the applicability of these ecological and social correlates to explaining the tremendous interspecific diversity of this appendage. To investigate the potential drivers of rodent tail morphology at a macroevolutionary level, we first carefully reviewed the literature and constructed a list of major hypotheses regarding this variation. We then compiled a database of 11 different tail traits related to length, color, texture, and ecological characteristics for 2,101 species of rodents (order Rodentia) and examined their key evolutionary correlates. Using Bayesian phylogenetic mixed models across the entire order and additionally within the five rodent suborders, we found that tail length is correlated with both temperature (Allen's rule) and locomotory mode, that black tips are more common in brightly lit environments, that naked tails are often found in warmer climates, that fluffy-tipped tails are more common in smaller and/or arboreal species, that prehensility is predominant in arboreal species and/or species with longer tails, and that tail autotomy is more common in open environments. Most of our tested predictions, largely drawn from population-level studies, are not recapitulated across the entire order, potentially indicating a role of local ecological context in shaping tail morphology.

Detection of pathogenic Leptospira spp. in unconventional pets

Leptospirosis is a disease caused by Leptospira spp. responsible for considerable impacts on the public and animal health. In the past two decades, non-domesticated species of pets (unconventional pets) have become popular. However, the role of these unconventional pets on maintaining diseases still unclear. Therefore, the objective of this study was to survey the presence of Leptospira spp. DNA in unconventional pets. Samples of kidney tissues from 29 animals belonging to the Mammalia class (including Orders Carnivora, Lagomorpha and Rodentia) were analyzed for the presence of the gene lipL32. As a result, DNA of pathogenic Leptospira spp. from specie L. interrogans was detected in four (13,80%) of the analyzed samples: three from Oryctolagus cuniculus and one from Mesocricetus auratus. This study highlights the importance of epidemiological surveillance of leptospirosis, as it identified in species of unconventional pets, that may possibly act as reservoirs of Leptospira spp.

A recent gibbon ape leukemia virus germline integration in a rodent from New Guinea

Germline colonization by retroviruses results in the formation of endogenous retroviruses (ERVs). Most colonization's occurred millions of years ago. However, in the Australo-Papuan region (Australia and New Guinea), several recent germline colonization events have been discovered. The Wallace Line separates much of Southeast Asia from the Australo-Papuan region restricting faunal and pathogen dispersion. West of the Wallace Line, gibbon ape leukemia viruses (GALVs) have been isolated from captive gibbons. Two microbat species from China appear to have been infected naturally. East of Wallace's Line, the woolly monkey virus (a GALV) and the closely related koala retrovirus (KoRV) have been detected in eutherians and marsupials in the Australo-Papuan region, often vertically transmitted. The detected vertically transmitted GALV-like viruses in Australo-Papuan fauna compared to sporadic horizontal transmission in Southeast Asia and China suggest the GALV-KoRV clade originates in the former region and further models of early-stage genome colonization may be found. We screened 278 samples, seven bat and one rodent family endemic to the Australo-Papuan region and bat and rodent species found on both sides of the Wallace Line. We identified two rodents (Melomys) from Australia and Papua New Guinea and no bat species harboring GALV-like retroviruses. Melomys leucogaster from New Guinea harbored a genomically complete replication-competent retrovirus with a shared integration site among individuals. The integration was only present in some individuals of the species indicating this retrovirus is at the earliest stages of germline colonization of the Melomys genome, providing a new small wild mammal model of early-stage genome colonization.

Distribution and prevalence of Sin Nombre hantavirus in rodent species in eastern New Mexico.

Orthohantaviruses are diverse zoonotic RNA viruses. Small mammals, such as mice and rats are common chronic, asymptomatic hosts that transmit the virus through their feces and urine. In North America, hantavirus infection primarily causes hantavirus cardiopulmonary syndrome (HCPS), which has a mortality rate of nearly 36%. In the United States of America, New Mexico (NM) is leading the nation in the number of HCPS-reported cases (N = 129). However, no reported cases of HCPS have occurred within eastern NM. In this study, we assessed the prevalence of Sin Nombre virus (SNV) in rodent assemblages across eastern NM, using RT-qPCR. We screened for potential rodent hosts in the region, as well as identified areas that may pose significant infection risk to humans. We captured and collected blood and lung tissues from 738 rodents belonging to 23 species. 167 individuals from 16 different species were positive for SNV RNA by RT-qPCR, including 6 species unreported in the literature: Onychomys leucogaster (Northern grasshopper mouse), Dipodomys merriami (Merriam's kangaroo rat), Dipodomys ordii (Ord's kangaroo rat), Dipodomys spectabilis (Banner-tailed kangaroo rat), Perognathus flavus (Silky pocket mouse), and Chaetodipus hispidus (Hispid pocket mouse). The infection rates did not differ between sexes or rodent families (i.e., Cricetidae vs. Heteromyidae). Generalized linear model showed that disturbed habitat types positively influenced the prevalence of SNV at sites of survey. Overall, the results of this study indicate that many rodent species in east New Mexico have the potential to maintain SNV in the environment, but further research is needed to assess species specific infectivity mechanisms and potential risk to humans.

Cryptic Speciation and Characteristics of the Transition Bias Following an Example of the cytb Gene in Palearctic Mammals

A study of taxonomic differentiation and transition bias of the cytb gene, focusing on the early stages of speciation, was carried out in 15 subfamilies/families of five orders of Palearctic mammals. It was confirmed that the genetic differentiation among taxa of small and large mammals is shifted by the same taxonomic level, in which connection the period of cryptic speciation of Micromammalia (semi- and allospecific levels) corresponds to the divergence of type species in their genus within Macromammalia. In all cases, both transition bias and its evolutionary compensation took place. The novelty of the study also lies in the proof that the alignment of the transitions and transversion rates in evolutionary lineages has the pattern of a phase transition, and the frequency of transversions in short-cycle species of the orders Insectivora and Rodentia is higher than in long-cycle orders Artiodactyla, Carnivora and Chiroptera while with relative equality of transitions. The latter circumstance might be associated with the traits of metabolism and determines the characteristics of the molecular evolution of mammalian groups with short and long life cycles.

Теріофауна Лисої гори в Києві: ознаки збереженості та рівні синантропізації

The article describes the mammal fauna of Lysa Hora, one of the key natural sites of Kyiv within the Kyiv Plateau. The analysis of various sources (original data, literature, collections, and social networks) shows the presence of 24 species of 11 families of 6 orders, including 5 species from 3 families of insectivorans, 6 species from 1 family of bats, 1 species of hares, 7 species from 3 families of rodents, 4 species from 2 families of carnivorans, and 1 species of ungulates. The ratio of alien and domestic species is high (21%), but the proportion of species with conservation statuses is also high (50%). The most valuable component of the rare fauna is bats associated with tree stands and fortifications. In general, despite significant anthropogenic changes, the local mammal fauna, combined with other animal groups and flora, makes Lysa Hora one of the most valuable natural sites in Kyiv. The conservation of the fauna of Lysa Hora requires a number of restrictions on anthropogenic activities, including a ban on any forestry activities, restrictions on recreational press, which is provided for by the current zoning of the site and which should be enshrined in the Regulations on the Lysa Hora Regional Landscape Park and the Project for the organisation of its territory.

La presencia de monticulos tipo Mima en la Argentina en relación con roedores del género Ctenomys

The discovery of Mima mounds pocking the Pampean region in the south-east of San Luis, south of Córdoba and north of La Pampa, as well as in some Monte regions in Mendoza, confirms the hypothesis that fossorial rodents are the origin of this type of phenomenon and that such mounds are present in different regions of the world coinciding with the presence of families of fossorial rodents showing similar morphology and behavior.&#x0D; This similarity with geomyds of the United States and other families from West and South Africa, becomes evident in Argentine Ctenomydae, which activity is responsible for the formation of this type of relief, Which has nowadays disappeared in most of the central part of the country due to agricultural practices.&#x0D; The discovery of Mima mounds in Argentina unquestionably confirms the discussed origin of this type of topographic accident, which has been subject to the most varied interpretations.

A new mammalian universal primer for the mitochondrial cytochrome b locus

We designed a set of amplification primers to target the mitochondrial cytochrome b gene of the rodent genus Oligoryzomys. Combinations of two sets of primers successfully amplified complete mitochondrial and partial cytochrome b (MT-CYB), from not only Oligoryzomys, but also other mammalian species from the orders Rodentia, Didelphimorphia, Primates, Chiroptera, Cetacea, Carnivora, and Lagomorpha. Preliminary sequencing analyses revealed that these primers generate informative sequences for several mammalian species important for phylogenetic and species delimitation analyses.