Shrew Blarina Research Articles

Mammalian neurotoxins, Blarina paralytic peptides, cause hyperpolarization of human T-type Ca channel hCav3.2 activation

Among the rare venomous mammals, the short-tailed shrew Blarina brevicauda has been suggested to produce potent neurotoxins in its saliva to effectively capture prey. Several kallikrein-like lethal proteases have been identified, but the active substances of B.brevicauda remained unclear. Here, we report Blarina paralytic peptides (BPPs) 1 and 2 isolated from its submaxillary glands. Synthetic BPP2 showed mealworm paralysis and a hyperpolarization shift (-11mV) of a human T-type Ca2+ channel (hCav3.2) activation. The amino acid sequences of BPPs were similar to those of synenkephalins, which are precursors of brain opioid peptide hormones that are highly conserved among mammals. However, BPPs rather resembled centipede neurotoxic peptides SLPTXs in terms of disulfide bond connectivity and stereostructure. Our results suggested that the neurotoxin BPPs were the result of convergent evolution as homologs of nontoxic endogenous peptides that are widely conserved in mammals. This finding is of great interest from the viewpoint of the chemical evolution of vertebrate venoms.

Comparing Effectiveness of AHDriFT Systems and Sherman Traps for Surveying Small Mammals in Northeastern Indiana

Abstract Traditional small mammal survey methods (e.g., Sherman traps) are beneficial in certain conditions but tend to require substantial effort and funds and can introduce various biases. The recently described adapted-Hunt drift fence technique (AHDriFT) camera trap system (i.e., camera traps combined with drift fences) can survey small terrestrial vertebrates and does not require much time in the field. Our objective was to compare the efficiency and effectiveness of AHDriFT systems and traditional Sherman traps for surveying small mammal communities. We conducted surveys with both methods in four sites of varying habitat types at the Eagle Marsh Nature Preserve (Fort Wayne, Indiana) from February to July in 2020 and May to August in 2021. We conducted 640 trap nights (one trap set on one calendar night) of Sherman trap surveys and 551 trap nights of AHDriFT system surveys. We captured 192 small mammals of three species with Sherman traps and obtained 532 images of unique small mammal individuals of seven species with AHDriFT systems. Our AHDriFT systems resulted in two times greater species richness (Z = −6.21, P < 0.01), 16 times greater species evenness (Z = −4.83, P < 0.01), and 23 times greater Shannon's diversity values (Z = −4.87, P < 0.01) than Sherman traps. The AHDriFT systems also documented the presence of four species that the Sherman traps did not (northern short-tailed shrew Blarina brevicauda, common shrew Sorex cinereus, long-tailed weasel Neogale frenata, eastern chipmunk Tamias striatus). Overall, AHDriFT system surveys provided 1.5–5 times more observations per dollar spent and required 90% less time in the field than Sherman trap surveys. These results suggest that AHDriFT systems may be a more efficient and effective method of surveying small mammal communities.

Are Northern Harriers (Circus hudsonius) Facultative Specialists on Arvicoline Rodents in Midwestern Agroecosystems

We assessed geographic and temporal variation in diets of wintering Northern Harriers (Circus hudsonius) in western Indiana, U.S.A., using multivariate regression on counts of prey from pellets collected at communal roosts. Because there is no uniform method for determining the minimum number of individuals (MNI) contained in a pellet, we also assessed whether application of four different counting methods influenced our conclusions. We collected 821 Northern Harrier pellets from four roosts in 2018 and 2019. Pellet contents differed between years, months, and roost sites. Voles (Microtus spp.) were the most commonly occurring prey group at all roosts and in both years (range: 45–73%), but were encountered 35% less frequently than reported on average by other studies in the midwestern U.S.A. Accordingly, other small mammal prey groups became more important dietary components than reported by most other midwestern studies, including mice (Peromyscus; 5–16%), western harvest mice (Reithrodontomys megalotis; 4–14%), and northern short-tailed shrews (Blarina brevicauda; 8–18%). The four methods of counting MNI produced no discernible effects on our conclusions concerning pellet contents between months or roosts. Northern Harriers in western Indiana exhibited great diet flexibility, which likely reflects local prey populations and constraints of life in intensive agroecosystems.

Populations of Small Mammals, Tallgrass Prairie and Prescribed Fire: A Fire-Reversal Experiment

We sampled small mammals in burned and unburned tallgrass prairie by using three sites in each of two contiguous ungrazed experimental fire-reversal treatments during 1999-2010. One of the experimental treatments (001A to R20A) had been burned in spring for >20 years and then was switched to an unburned research treatment after the spring fire in 2000. In contrast, the other treatment (020A to R01A) had been left unburned for 20 of 29 years before it was switched to an annually burned treatment beginning with the prescribed fire in spring 2001. Overall, we recorded 11 species of rodents and two of shrews for a total of 2,444 individuals. The white-footed mouse (Peromyscus leucopus) was the most abundant species followed by the hispid cotton rat (Sigmodon hispidus) and deer mouse (P. maniculatus). Of the seven common species (>25 individuals), six were strongly associated with one of the treatments, and several species showed positive associations with some part of the landscape within each treatment. Furthermore, white-footed mice, deer mice, prairie voles (Microtus ochrogaster), western harvest mice (Reithrodontomys megalotis) and Elliot's short-tailed shrews (Blarina hylophaga) showed significant temporal patterns of abundance in either R01A or R20A in one or both seasons (autumn or spring). Our study also supports a very important conservation message. That is, the white-footed mouse (a woodland species) and the hispid cotton rat (a colonizing species) were more numerically dominant than the most common rodent, the deer mouse, (a native prairie species) throughout the 10-year study. These observations demonstrate that areas not burned frequently allow encroachment by shrubs and then trees, which subsequently allow the white-footed mouse and hispid cotton rat to expand into these areas. Conversely, the stoppage of frequent fires ultimately degrades the mosaic of prairie habitats for native prairie small mammals [such as the deer mouse, prairie vole and western and plains harvest mice (R. montanus)] and these species move out as shrubs and trees become common. Visual observations indicate that the latter (degradation of native tallgrass prairie) occurs much more rapidly (potentially within a decade) than the restoration of native tallgrass prairie by the elimination of shrubs and trees by annual burning (potentially 50 or more years).

Structural and functional characterization of enamel pigmentation in shrews

Pigmented tooth enamel occurs in several vertebrate clades, ranging from mammals to fish. Although an iron compound is associated with this orange to red colored pigmentation, its chemical and structural organization within the enamel is unknown. To determine the nature of the iron compound, we investigated heavily pigmented teeth of the northern short-tailed shrew Blarina brevicauda using combined characterization techniques such as scanning and transmission electron microscopy and synchrotron X-ray diffraction. We found that the pigmentation of the enamel with an iron content of around 8wt% results from a close to amorphous magnetite phase deposited around the nm-sized enamel crystals. Furthermore, the influence of the pigmentation on the enamel hardness was determined by nanoindentation measurements. Finally, the biomechanical function and biological context are discussed in light of the obtained results.

A Large Number of Southern Short-Tailed Shrew, Blarina carolinensis, Skulls Recovered From a Single Discarded Bottle

Abstract The recovery of 25 southern short-tailed shrew (Blarina carolinensis) skulls from a single discarded bottle in Louisiana appears to be the largest number of Blarina ever found in one bottle and reported in the literature. Conservation concerns about the impact of discarded bottles on small mammal faunas seem justified and warrant investigation.

Short-term responses of small mammals to timber harvest in the United States Central Hardwood Forest Region

Identifying the effect of timber harvest on plant and animal communities is important for managers seeking to conserve ecosystem function. Timber harvest affects many forest species, including small mammals, a key component of forest food webs. We studied short-term responses of several common small-mammal species to clearcutting and shelterwood harvest in hardwood forests of southern Indiana. We trapped small mammals at 32 forest stands for 2 years before harvest. Each stand then received a timber harvest treatment: either the creation of a 0.4-, 2-, or 4-ha clearcut opening, shelterwood harvest, or no harvest. Following harvest, we trapped small mammals for 3 additional years. We estimated abundance from capture data and compared estimates before and after harvests using an N-mixture model fit in a Bayesian framework. Small mammals in our study differed in their responses to timber harvest. Eastern chipmunks (Tamias striatus) increased in all clearcut opening sizes, whereas white-footed mice (Peromyscus leucopus) and short-tailed shrews (Blarina brevicauda) were less abundant in larger clearcuts. The first stage (midstory removal) of a 3-stage shelterwood harvest had no impact on the small-mammal community. Mast production influenced small-mammal populations independent of silvicultural treatments. In the years immediately following harvest, managers can expect populations of common small-mammal species to increase or remain unchanged in small clearcut openings, but some species decline in larger openings that reduce the edge to interior ratio of habitat created. The phased shelterwood harvest system in which habitat is altered over a longer period may be ideal for maintaining existing small-mammal populations. © 2013 The Wildlife Society.

Multiple factors limit use of local sites by Elliot’s short-tailed shrews (Blarina hylophaga) in tallgrass prairie

Spatial variation in abundance has been attributed to habitat heterogeneity and patchiness. Our goal in this research was to understand what factors were associated with spatial patterns of habitat use by Elliot’s short-tailed shrews ( Blarina hylophaga Elliot, 1899) in tallgrass prairie. Our modeling efforts were based on 20 years (1981–2000) of presence–absence data for shrews at each of 20 stations (local site) along 14 permanent traplines on Konza Prairie Biological Station, Kansas, USA. A logistic model accurately predicted the presence of short-tailed shrews at a local site. Probability of shrew occurrence decreased as amount of precipitation decreased, slope steepness increased, grazing increased, or burned area within 500 m of a local site increased. However, when amount of precipitation was low, area burned was high, or grazing occurred, shrews were uncommon and responded little to the other variables. Numbers of shrews were negatively related only to numbers of deer mice ( Peromyscus maniculatus (Wagner, 1845)), a mouse that selects burned and grazed habitats that shrews avoid. Our observations suggest that multiple environmental factors limit use of local sites, whereas competition with other species does not. Our results can inform decisions related to conservation of biodiversity given management practices in this endangered ecosystem.

Multiple captures provide evidence of small mammal social behavior

Social behavior of small mammals living under natural conditions often is inferred from live-trapping data, particularly from incidents in which two or more individuals are captured together in a trap. We examined whether multiple-capture data from a long-term study of prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) were consistent with well-known species differences in social behavior (whereas prairie voles are highly social and display monogamy, meadow voles are less social and promiscuous). When possible, we also examined multiple captures of two nontarget species, northern short-tailed shrews (Blarina brevicauda) and western harvest mice (Reithrodontomys megalotis). Percent of total captures that were multiple captures and percent of total adult captures that were male–female captures were highest for prairie voles and lowest for meadow voles; values for harvest mice and shrews were in between those of the vole species, but more similar to values for meadow voles. Repeat captures of the same male–female pair occurred most commonly in prairie voles, and multiple captures of this species typically involved individuals from the same social group. Multiple captures of adults and juveniles were more common in prairie voles than meadow voles, except for captures of at least one adult male and at least one juvenile, which did not differ between the two vole species. Multiple capture data for prairie voles and meadow voles were largely consistent with established species differences in social behavior, suggesting that such data can provide an accurate indication of social and mating systems of small mammals.

Convergent Evolution of Novel Protein Function in Shrew and Lizard Venom

How do proteins evolve novel functions? To address this question, we are studying the evolution of a mammalian toxin, the serine protease BLTX [1], from the salivary glands of the North American shrew Blarina brevicauda. Here, we examine the molecular changes responsible for promoting BLTX toxicity. First, we show that regulatory loops surrounding the BLTX active site have evolved adaptively via acquisition of small insertions and subsequent accelerated sequence evolution. Second, these mutations introduce a novel chemical environment into the catalytic cleft of BLTX. Third, molecular-dynamic simulations show that the observed changes create a novel chemical and physical topology consistent with increased enzyme catalysis. Finally, we show that a toxic serine protease from the Mexican beaded lizard (GTX) [2] has evolved convergently through almost identical functional changes. Together, these results suggest that the evolution of toxicity might be predictable-arising via adaptive structural modification of analogous labile regulatory loops of an ancestral serine protease-and thus might aid in the identification of other toxic proteins.

SIGNIFICANCE OF BLARINA BREVICAUDA AS A PREDATOR AND SOURCE OF TRAP-CAPTURE BIAS ON SMALL MAMMALS

Evidence on whether the northern short-tailed shrew (Blarina brevicauda) is a significant predator or a source of bias in trap-capture success of small mammals is contradictory. We compared subsequent captures of 2 murid rodent species (Clethrionomys gapperi and Peromyscus maniculatus) after capture of either murid species or B. brevicauda by using 4 years of capture-release data from New Brunswick, Canada. Capture success for P. maniculatus in a trap after occupancy by B. brevicauda was 65% lower than expected, and for C. gapperi, 67% lower than expected. The response by C. gapperi and P. maniculatus to odors of a different species was similar to their response to odor of B. brevicauda. Although we conclude that examination of odor-response data does not permit a conclusion as to whether B. brevicauda is a significant predator, the ubiquitous distribution of B. brevicauda implies that their influence on trap-capture success is significant, particularly in forests where small-rodent species are of similar weight to B. brevicauda.

POPULATION DYNAMICS AND ACTIVITY OF SOUTHERN SHORT-TAILED SHREWS (BLARINA CAROLINENSIS) IN SOUTHERN ILLINOIS

We captured, marked, and recaptured southern short-tailed shrews (Blarina carolinensis) during a 30-month livetrapping study in a woodlot in Jackson County, Illinois, to compare aspects of their life history with those of the northern short-tailed shrew (B. brevicauda). A total of 106,496 trap checks (15,782 trap nights) resulted in 3,430 captures of 313 B. carolinensis from February 1996 through August 1998. Trapping mortality was only 18 individuals. Sex ratio did not differ from 1:1. Estimated population density peaked at 57 individuals/ha in late summer and autumn then declined during winter. Recruitment, including birth and immigration, peaked in spring and late summer each year. Individuals entering the population in the spring and early summer had higher survival rates than those entering in the autumn. A weak correlation was found between recruitment and precipitation, and between population density and humidity. Shrew activity (timing of captures) showed significant relationships with light condition and season. During summer, shrews were caught more frequently at night. In the winter, they were captured more frequently during the day. Capture rate was negatively related to precipitation and positively related to humidity. Population dynamics and activity patterns were similar to those of B. brevicauda.

ECTOPARASITES AND FOOD HABITS OF ELLIOT'S SHORT-TAILED SHREW, BLARINA HYLOPHAGA

Abstract The natural history of Elliot's short-tailed shrew (Blarina hylophaga) has remained virtually unknown since it was recognized as a distinct species in 1981. For this study, we examined 26 specimens of B. hylophaga for ectoparasites. We found 5 species of fleas, 1 species of tick, and 17 species of mites. We also examined stomach contents of 30 specimens of B. hylophaga and discovered that insects (particularly beetles), slugs, and spiders were the most common food items. To determine the degree of similarity between B. hylophaga and the 2 other widely distributed short-tailed shrews, we compared these data to the published ectoparasite and food habits data for B. carolinensis and B. brevicauda. We found that both the ectoparasitic fauna and the diet of B. hylophaga broadly overlap those of its congeners. We also noted, however, that each species of Blarina had parasites that were more closely associated with it than with the other 2 species of Blarina. In addition, the diet of B. hylophaga consis...

Purification and characterisation of blarinasin, a new tissue kallikrein-like protease from the short-tailed shrew Blarina brevicauda: comparative studies with blarina toxin

A new tissue kallikrein-like protease, blarinasin, has been purified from the salivary glands of the short-tailed shrew Blarina brevicauda. Blarinasin is a 32-kDa N-glycosylated protease with isoelectric values ranging between 5.3 and 5.7, and an optimum pH of 8.5 for enzyme activity. The cloned blarinasin cDNA coded for a pre-pro-sequence and a mature peptide of 252 amino acids with a catalytic triad typical for serine proteases and 43.7-54.0% identity to other mammalian tissue kallikreins. Blarinasin preferentially hydrolysed Pro-Phe-Arg-4-methylcoumaryl-7-amide (MCA) and N-tert-butyloxycarbonyl-Val-Leu-Lys-MCA, and preferentially converted human high-molecular-weight kininogen (HK) to bradykinin. The activity of blarinasin was prominently inhibited by aprotinin (K(i) =3.4 nM). A similar kallikrein-like protease, the lethal venom blarina toxin, has previously been purified from the salivary glands of the shrew Blarina and shows 67.9% identity to blarinasin. However, blarinasin was not toxic in mice. Blarinasin is a very abundant kallikrein-like protease and represents 70-75% of kallikrein-like enzymes in the salivary gland of B. brevicauda.

Attempted isolation ofBlastomyces dermatitidisfrom native shrews in northern Wisconsin, USA

The precise ecological niche of Blastomyces dermatitidis is unknown. The related dimorphic fungus, Paracoccidioides brasiliensis, has been isolated from South American ground-dwelling insectivorous armadillos. We attempted to isolate Blastomyces from shrews, North American ground-dwelling insectivores that have been shown to harbor Histoplasma capsulatum in endemic areas. Forty-seven masked shrews (Sorex cinereus) and 13 northern short-tailed shrews (Blarina brevicauda) were collected in endemic areas of northern Wisconsin and Michigan using pitfall traps. Specimens were collected between 1998 and summer 2002, stored frozen, then necropsied. Cultures of nasopharynx, lungs, liver, spleen and large and small bowel were placed on yeast extract phosphate agar with one or two drops of ammonium hydroxide. Cultures for Blastomyces were negative from all 60 shrews and two deer mice (Peromyscus maniculatus) and three southern red-backed voles (Clethrionomys gapperi), which were trapped inadvertently. Histological examination of 36 of these specimens revealed no Blastomyces yeast forms. Northern Wisconsin shrews do not appear to be carriers of B. dermatitidis.

A preliminary note on banded karyotypes of the short-tailed shrewBlarina brevicauda(Mammalia, Insectivora)

Chromosomes of the short-tailed shrew Blarina brevicauda ,w hich dis- play the numerical polymorphism arisen from Robertsonian rearrangements, were analyzed with conventional and silver staining and G- and C-banding techniques. With respect to all specimens examined in the present study, the diploid chromosome number (2n) and fundamental autosomal arm number (FN) were 50 and 48, respectively. The karyotype consisted of 24 pairs of acro- centric autosomes, a large-sized metacentric X chromosome, and a small-sized submetacentric Y chromosome. The comparison with previous findings sug- gested the geographic polymorphism of Y chromosome in this species. All autosomes and the X chromosome carried slight centromeric constitutive het- erochromatin, whereas the Y chromosome was entirely heterochromatic. On the satellites of short arms of two autosomal pairs, the nucleolus organizer regions (NORs) were recognized. The G- and C-banded and Ag-NOR-stained kary- otypes presented in the present study could be useful cytogenetic characteristics for specification of chromosomes participating in Robertsonian rearrangements within this species and for karyo-systematic study of genus Blarina.

Allozyme differentiation in five species of North American shrews (Soricidae: Mammalia)

Starch gel electrophoresis was used to investigate patterns of genetic variation in five species of shrews from southern Illinois, and western Kentucky and Tennessee. Four of the five species occur sympatrically. Twenty-eight presumptive loci were examined in the following species: pygmy shrew Sorex hoyi Baird, southeastern shrew Sorex longirostris, northern short-tailed shrew Blarina brevicauda, southern short-tailed shrew Blarina carolinensis, and least shrew Cryptotis parva. Of the 28 loci, 11 were monomorphic for the same allele in all species. Only one locus ( Mpi) was diagnostic, with a different allele for each species. At two other loci ( Est and PepD) the two species of Blarina also demonstrated significant differences. These three loci could be used to distinguish the two morphologically very similar species of Blarina. The mean heterozygosity values for B. brevicauda and S. hoyi were higher than previously reported. Levels of heterozygosity did not show a correlation with known degree of habitat specialization in the five species. Genetic distance analysis demonstrated greater genetic similarity between the two Blarina species than the two Sorex species. A dendrogram produced from a genetic distance matrix is consistent with current views of soricid phylogeny.

Long-Term Variation in Abundance of Elliot's Short-Tailed Shrew (Blarina hylophaga) in Tallgrass Prairie

Long-Term Variation in Abundance of Elliot's Short-Tailed Shrew (Blarina hylophaga) in Tallgrass Prairie

Morphological and Mitochondrial DNA Variation in a Hybrid Zone Between Short-Tailed Shrews (Blarina) in Nebraska

The parapatric boundary separating Blarina brevicauda and B. hylophaga in Nebraska was analyzed to quantify hybridization. Multivariate analyses of morphological data from 88 reference animals and 715 shrews from two transects across the boundary found the species to be distinct; 49 animals, however, were morphologically intermediate and could not be identified to species. Those individuals were trapped at locations clustered near the line of contact, suggesting that they were hybrids. Hybrids of trappable age apparently do not suffer reduced survival rates but appear to be reproductively less fit than nonhybrids. The small number of hybrids found, the abrupt nature of the boundary, and the strong similarity of clines for different characters within transects suggests genetic exchange between the species is limited. Genetic analyses were conducted on 190 shrews from the boundary and 61 reference animals. Restriction-site analysis of the mitochondrial cytochrome b gene generated diagnostic patterns for the reference samples with two separate enzymes. From the boundary, 17 hybrids were found, recognizable by conflicting morphological and mitochondrial characteristics. Those individuals were not morphologically intermediate and probably represented second generation or back-cross hybrids, indicating Fl hybrids are not sterile. Data also indicate that interspecific mating involves females of both species. Overall, these analyses suggest that a lack of assortative mating, combined with selection against hybrids, may act to limit sympatry between these species. Given the number of parapatric boundaries present in Blarina , the fossil-based evolutionary history proposed, and the morphological differences of extant species, this group might represent a model system for hybrid zone research.

Microhabitat selection by small mammals in a southern Appalachian fen in the USA

Little ecological information is available on small mammals inhabiting wetlands in the southern Appalachian mountains of the USA. These wetland systems are becoming rare features in southern landscapes due to human activities. We investigated the small mammal fauna and examined the microhabitat associations of the two most abundant species in a southern Appalachian fen. Four species of small mammals were captured: the meadow jumping mouse (Zapus hudsonius), short-tailed shrew ( Blarina brevicauda), white-footed mouse ( Peromyscus leucopus), and golden mouse ( Ochrotomys nuttalli). Peromyscus and Ochrotomys, which were caught in the largest numbers, preferred sites characterized by moderate herbaceous cover and substantial canopy closure. Peromyscus, however, selected areas with greater canopy closure and higher tree densities, suggesting that they are greater habitat specialists than Ochrotomys in this wetland community.