Development of a morphological key for the southern salt marsh harvest mouse using genetically verified individuals

The salt marsh harvest mouse (SMHM; Reithrodontomys raviventris) is a state and federally listed endangered species endemic to the coastal marshes of the San Francisco Estuary of California. Of two subspecies, the southern (R. r. raviventris) is most endangered and lacks reliable morphological field tools to distinguish from the sympatric western harvest mouse (WHM; R. megalotis). We trapped and collected genetic samples and morphological data from 204 harvest mice from 14 locations from across the range of the southern SMHM. Genetic species identification indicated these to be composed of 48 SMHM and 156 WHM, which we compared at ten morphological characters. Most continuous characters overlapped between species. Color characters were significantly differentiated and we identified a number of species-specific diagnostic pelage categories in both species. A random forest analysis indicated that ventral coloration of the abdomen and the ventral tail hair color were the most useful for differentiating between species. We used these two morphological characters to develop a decision tree which correctly classified 94% of harvest mice to species with 99% accuracy. These findings suggest that our decision tree can be used to reliably identify the species of most harvest mice in the range of the southern SMHM, with a small proportion (6% in our study) needing genetic confirmation. The decision tree should be tested on additional harvest mice that were not used in its development, particularly from novel locations across the range.

The first description of the nymphal stages of Hoplopleura longula (Psocodea: Anoplura: Hoplopleuridae) from the harvest mouse Micromys minutus (Rodentia: Muridae)

Despite the widespread belief that an extensive body of knowledge exists for the sucking lice (Anoplura), some of their common, Eurasian or even cosmopolitan species still lack complete taxonomic descriptions, especially those for their nymphal stages. This applies especially to the most common rodent parasites: the lice of the genus Hoplopleura. In Europe, only two of the five most common Hoplopleura species have full taxonomic characteristics with a description of the nymphal stages. This study enriches the current state of knowledge for another species, Hoplopleura longula and presents the first description of its nymphal stages. The study includes five rare louse specimens (two nymphs I, one nymph II, two nymphs III) of H. longula collected from 63 Eurasian harvest mice Micromys minutus. The collected lice were fixed and preserved in 70% ethyl alcohol solution and then placed in polyvinyl-lactophenol to form total preparations. Only two of the five species found in Eurasia (H. acanthopus, H. affinis, H. captiosa, H. edentula and H. longula) have been given full taxonomic descriptions, including immature stages. This paper presents a description of the nymphal stages of H. longula (described for the first time).

Seasonal patterns in habitat use by the harvest mouse (Micromys minutus) and other small mammals

The ecology of the harvest mouse (Micromys minutus) is poorly understood, partly because it is a difficult species to monitor. It is commonly associated with reedbeds, where evidence suggests that it experiences strong seasonal fluctuations in abundance. However, it is unknown whether these fluctuations are caused by real changes in population size, or by movement between habitats. This study investigated seasonal changes in population size and habitat use by harvest mice, and other small mammal species, by trapping the reedbed and three associated habitat types: woodland, pasture and arable land. A sampling effort of 9887 trap bouts across nine months, resulted in 70 captures of harvest mice, as well as wood mice (N = 1022), bank voles (N = 252), field voles (N = 9), common shrews (N = 86) and pygmy shrews (N = 7). The reedbed was the habitat with the most captures and highest diversity. Harvest mice were caught exclusively in the reedbed at the beginning of autumn. Wood mice and bank voles experienced fluctuations in population numbers and wood mice also showed seasonal variation in habitat use. Our study supports the idea that harvest mice undergo extreme seasonal fluctuations in abundance in reedbeds, but these do not appear to be related to changes in habitat use.

Reithrodontomys mexicanus (Rodentia: Cricetidae)

Reithrodontomys mexicanus (Saussure, 1860) is a cricetid rodent commonly called the Mexican harvest mouse and is one of 24 recognized species in the genus. It has grooved upper incisors distinctive of Reithrodontomys, and a medium to relatively large size, with tail longer than head and body; dorsal pelage varies from brown to cinnamon orange. It is distributed from Mexico to Nicaragua and in the northwestern region of South America. It occupies different habitats including humid pine-oak forests, cloud forests, and deciduous forests at elevations from about 1,000 to 3,800 m. R. mexicanus is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources, although information about population size throughout its distribution range is unknown.

Findings of overground nests of rodents in the Ukrainian Beskids (upper course of the Dnister)

Materials are collected and generalised on the overground nesting activity of 4 rodent species under conditions of the north Carpathian taiga: the red squirrel (Sciurus vulgaris), the edible dormouse (Glis glis), the hazel dormouse (Muscardinus avellanarius), and the harvest mouse (Micromys minutus). The locality is characterised by a combination various habitats. Common and unique variants of nests of these species are described, particularly the arrangement by the hazel dormouse of its own nests in nests of the Eurasian wren and song thrush, an unusual nest of the red squirrel, and the nesting of the edible dormouse in an abandoned dress.

Improving detectability of the harvest mouse (Micromys minutus Pallas, 1771) by above ground live-trapping

Harvest mouse detectability represents a real issue for surveys, as usual ground-trap monitoring is known to fail to detect this species, especially in summer. The present study proposes to test ground versus aerial live-trapping efficiency for harvest mouse in summer, with a trapping design using paired ground and aerial traps over a 2-year survey in a reedbed. Over 10,720 trap-nights, the harvest mouse represented 85% of the 1078 small mammals captured, and it was the only species among five which was more often trapped above ground (n = 702) than on the ground (n = 213). Capture probability was significantly higher in aerial than in ground traps, with a slightly positive effect of leaf litter and, surprisingly, a negative effect of dense vegetation cover. Following these results, recommendations are made for harvest mouse monitoring.