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Knowledge on the mating system of a species is central to understand population dynamics and development. Special attention has been paid to the investigation of monogamous species and evolutionary causes and advantages of this mating system. However, social monogamy does not necessarily imply also genetic monogamy. Given the rarity of genetic monogamy in mammal species and the uncertain conclusions regarding multiple paternity in Eurasian beavers (Castor fiber), here, we undertake a further attempt to clarify the genetic monogamy of Eurasian beavers studying an Austrian beaver population by genotyping of gestating females and their foetuses at 19 microsatellite loci. Microsatellite analysis of mother–offspring groups suggest the occurrence of multiple paternity at a low level: two out of 42 litters (4.8%) were sired by two different males. We discuss the occurrence of extra-pair mating and potential drivers of multiple paternity in the light of beaver biology, population densities, territory characteristics and resulting activity ranges during reproduction period. Especially in the context of increasing beaver population densities in recovering populations and related increase of human-wildlife conflicts, sound knowledge on breeding biology, including species-specific reproduction tactics and their general applicability, is important for population monitoring. [ABSTRACT FROM AUTHOR]

The purpose of this Nomenclatural Note is to demonstrate that 1) the objective junior synonym Trogontherium cuvieriFischer, 1814 should have precedence over Castor trogontheriumCuvier, 1809, and 2) the binomen should be attributed to Fischer (1814) instead of the widely cited Fischer (1809). When, in 1809, Johann Gotthelf Fischer described the fossil skull of a beaver found near the Sea of Azov (Russia), he erected for it the genus name Trogontherium without proposing a species name. The skull later became the holotype of what is now commonly cited as Trogontherium cuvieri Fischer, 1809, even though this binomen had not been formally proposed that year. Later that year, Georges Cuvier used the name Castor trogontherium to refer to the same specimen. We found an apparently previously-overlooked 1814 publication by Fischer in which the binomen Trogontherium cuvieri was used for the first time. Although an objective junior synonym of Castor trogontheriumCuvier, 1809, that senior synonym has not been used as a valid name since 1884 and, in compliance with the Code, we suggest reversing precedence and conclude that the correct name for the European giant beaver is Trogontherium cuvieriFischer, 1814. [ABSTRACT FROM AUTHOR]

In this study, we describe the dental remains of a very minute beaver from the early Late Miocene locality Hammerschmiede (MN 7/8) located at the Northern Alpine Foreland Basin (Southern Germany, Bavaria). The finds represent the so far most comprehensive (>1.000 dental specimens) collection of the trogontheriine castorid Euroxenomys minutus. Metrically and morphologically, the large data set demonstrates an extensive intraspecific variability of this beaver from Hammerschmiede that covers most finds of other European localities and confirms previous species assignments. The subspecies Euroxenomys minutus rhenanus from Dorn-Dürkheim (Germany), clearly isolates from this range of variation and can thus be validated. The performed age-frequency distributions for Euroxenomys minutus from the local stratigraphic levels HAM 5 (rivulet) and HAM 4 (river) correspond roughly and also resemble Euroxenomys from the swamp deposit Rudabánya (Hungary). Since previous mortality studies on the also occurring larger beaver Steneofiber depereti from Hammerschmiede demonstrated dominance of behavioural or internal factors, this cross-ecosystem similarity in mortality for the small beaver species is likely explained by external factors, such as predation. Supported by a taphonomic bone analysis, a multitude of predators are finally considered to prey on Euroxenomys minutus and indicate a predatory bone assemblage. [ABSTRACT FROM AUTHOR]

Dental remains of a medium sized beaver from the early Late Miocene Hammerschmiede locality (MN 7/8) in the Northern Alpine Foreland Basin (Southern Germany, Bavaria) are described and assigned to Steneofiber depereti. The numerous material (160 teeth) was collected in the two fossiliferous layers HAM 5 and HAM 4 and comprises beaver individuals of a large range of age classes, from juvenile to old. The dental remains metrically and morphologically overlap the stratigraphic older Steneofiber spp. and the younger Chalicomys spp. This supports the hypothesis of the European anagenetic evolutionary lineage Steneofiber depereti–Chalicomys jaegeri. The morphological characters to differentiate Steneofiber depereti and Chalicomys jaegeri are discussed and redefined. The performed age-frequency distribution (Mortality profile) indicates a natural ecological mortality and confirms that at least the fluvial channel of the HAM 4 deposits was the actual optimal beaver habitat and continuously populated by larger family groups of beavers. Furthermore, there are indications that the Hammerschmiede beaver had a similar parental investment as today’s beavers, where young adults migrate to poorer habitats in the second year, in search of their own territory. The shallower channel of HAM 5 possibly represents such a “second choice” habitat.

Dental remains of a medium sized beaver from the early Late Miocene Hammerschmiede locality (MN 7/8) in the Northern Alpine Foreland Basin (Southern Germany, Bavaria) are described and assigned to Steneofiber depereti. The numerous material (160 teeth) was collected in the two fossiliferous layers HAM 5 and HAM 4 and comprises beaver individuals of a large range of age classes, from juvenile to old. The dental remains metrically and morphologically overlap the stratigraphic older Steneofiber spp. and the younger Chalicomys spp. This supports the hypothesis of the European anagenetic evolutionary lineage Steneofiber depereti-Chalicomys jaegeri. The morphological characters to differentiate Steneofiber depereti and Chalicomys jaegeri are discussed and redefined. The performed age-frequency distribution (Mortality profile) indicates a natural ecological mortality and confirms that at least the fluvial channel of the HAM 4 deposits was the actual optimal beaver habitat and continuously populated by larger family groups of beavers. Furthermore, there are indications that the Hammerschmiede beaver had a similar parental investment as today's beavers, where young adults migrate to poorer habitats in the second year, in search of their own territory. The shallower channel of HAM 5 possibly represents such a "second choice" habitat. [ABSTRACT FROM AUTHOR]

Two genera of Miocene beavers (Castoridae), Hystricops and Priusaulax are referred to a new tribe Hystricopini of the subfamily of giant beavers, Castoroidinae based on cranial and dental morphologies. Previously undescribed and more complete specimens of Hystricops demonstrate that it is referable to the Castoroidinae rather than the Castorinae. Along with Priusaulax, it is believed to represent a group of basal castoroidines, distinct from later Castoroidinae by the retention of the primitive morphology of the contact of the lacrimal bone with the jugal on the cranium, as well as more primitive dental morphologies (lower crown-height and simple occlusal pattern of cheek teeth). A partial cranium and several isolated teeth from the Hemingfordian of Colorado, originally referred to Anchitheriomys?, are referred here to a new species, Priusaulax wilsoni sp. nov. Monosaulax senrudi from the Barstovian of Montana is also referred to Priusaulax. Hystricops is limited to the type species H. venustus from the Clarendonian and Barstovian North American Land Mammal Age (NALMA), and H. browni from the Hemphillian NALMA.

Po vrnitvi bobra leta 1998 v Slovenijo in njegovem hitrem širjenju novejših podatkov o razširjenosti in velikosti populacije za to vrsto ni. V obdobju od februarja 2017 do maja 2017 smo pregledali celoten tok reke Krke s pritoki in popisali bobrišča. Število in lokacije novih bobrišč dokazujejo, da se je število bobrov na Krki povečalo. Obrežna vegetacija z velikimi drevesi majhnega premera in dovolj bogata zeliščna plast sta ključna dejavnika bobrove razširjenosti v tem delu Slovenije. Med popisom smo na nekaj območjih našli tudi bobrove jezove, ki so bili pretežno majhni, a bobrom omogočajo preživetje tudi v manjših pritokih. Po opisanih skupno 56 bobriščih smo ocenili, da je v letu 2017 celotna populacija na reki Krki s pritoki štela 168–392 osebkov.

Two genera of Miocene beavers (Castoridae), Hystricops and Priusaulax are referred to a new tribe Hystricopini of the subfamily of giant beavers, Castoroidinae based on cranial and dental morphologies. Previously undescribed and more complete specimens of Hystricops demonstrate that it is referable to the Castoroidinae rather than the Castorinae. Along with Priusaulax, it is believed to represent a group of basal castoroidines, distinct from later Castoroidinae by the retention of the primitive morphology of the contact of the lacrimal bone with the jugal on the cranium, as well as more primitive dental morphologies (lower crown-height and simple occlusal pattern of cheek teeth). A partial cranium and several isolated teeth from the Hemingfordian of Colorado, originally referred to Anchitheriomys?, are referred here to a new species, Priusaulax wilsoni sp. nov. Monosaulax senrudi from the Barstovian of Montana is also referred to Priusaulax. Hystricops is limited to the type species H. venustus from the Clarendonian and Barstovian North American Land Mammal Age (NALMA), and H. browni from the Hemphillian NALMA. [ABSTRACT FROM AUTHOR]

Two large rodents from the Middle Miocene (13.0–12.4 Ma) were discovered at the Chiang Muan Coal Mine, northern Thailand. One, a beaver (Anchitheriomys, Castoridae), has large cheek teeth with a high crown, the crown base wider buccolingually, basically six fossettes/sinuses, enamel foldings strongly complicated, and hypoflexus/flexid shallow dorsoventrally. Based on dental morphology, this form is more similar toAnchitheriomys suevicusfrom Europe than toAnchitheriomys tungurensisfrom northern China. The other species is considerably larger thanAnchitheriomys, based on incisor measurements, and lacks longitudinal grooves or deep ridges on the enamel surface, which are diagnostic ofAnchitheriomys. Furthermore, the inner enamel observed by scanning electron microscope has uniserial Hunter-Schreger bands, similar to castorids rather than hystricids. This species is indeterminate taxonomically, but differs from any rodents known from Asia. The distribution ofAnchitheriomyswas previously restricted between the latitudes 30°N and 50°N, but this occurrence in northern Thailand at low latitude (ca. 19°N) suggests that it had wider distribution on the Eurasian continent. [ABSTRACT FROM PUBLISHER]

Abstract: The first biplanar X-ray motion analysis of mastication and food processing for Castor fiber is presented. While particles are chipped off interaction of incisors involves variable movements of the lower mandible and thus incisors. After jaw opening the tip of the lower incisors can reach different positions anteriorly of the upper incisors. Then the mandible moves upwards and backwards and brings the tips of the incisors into contact. The lower incisors slide along the wear facet of the upper to the ledge when the cheek teeth occlude. The glenoid fossa and lower jaw condyle are in close contact during incisor contact and no transverse movements are observed. Mastication involves interaction of the cheek teeth with no contact of the incisors. When the cheek teeth are in occlusal contact the mandible is moved forward and transverse, or mediolateral. In consecutive power strokes the jaw is moved alternately to the right and left side. When the jaw opens it is brought into a more central but not totally centred position. During mastication the condyles are positioned posteriorly to the glenoid allowing lateral movement of the mandible. The lateral movement is particularly noticeable in the anterior part of the mandible. With the lateral movements of the incisors one glenoid has to move posteriorly, the other anteriorly. [Copyright &y& Elsevier]

Beavers strongly modify their environment by not only building dams and creating ponds, which slow the water flow, but also by selective cutting and removing of trees, which change the spatial structure of the forest. We aimed to test the hypothesis that beaver activity promotes new foraging sites for insectivorous bats. The beaver's influence can be especially significant on aerial hawkers that prefer moderate structural clutter, like the Pipistrellus species (by creating new canopy gaps), and on water-surface foragers, like Myotis daubentonii (by creating ponds with smooth water surface). The study was conducted on small streams in forest areas of northern Poland, which were colonized by the European beaver (Castor fiber). Bat activity was recorded with a Pettersson D-980 ultrasound detector on line transects. The number of bat passes was significantly higher in the stream sections modified by beavers (flooded and subjected to intensive tree cutting) than in the unmodified sections (for Pipistrellus nathusii, Pipistrellus pipistrellus, Pipistrellus pygmaeus, Nyctalus noctula, and all species lumped together). Contrary to our expectations, the activity of the Myotis species was significantly lower on the transect with the largest beaver ponds, possibly due to the blanket of duckweed (Lemnaceae), which is known to produce clutter echoes, thereby reducing prey detection by echolocating M. daubentonii. [ABSTRACT FROM AUTHOR]

Glires represent a eutherian clade consisting of rodents and lagomorphs (hares, rabbits, and pikas). Chromosome evolution of Glires is known to have variable rates in different groups: from slowly evolving lagomorphs and squirrels to extremely rapidly evolving muroids. Previous interordinal homology maps between slowly evolving Glires were based on comparison with humans. Here, we used sets of chromosome-specific probes from Tamias sibiricus (Sciuridae), Castor fiber (Castoridae) and humans to study karyotypes of six ground squirrels (genera Marmota and Spermophilus) and one tree squirrel (genus Sciurus), mountain hare (genus Lepus), and rabbit (genus Oryctolagus). These data supplemented with GTG banding comparisons allowed us to build comparative chromosome maps. Our data showed the absence of previously found squirrel associations HSA 1/8 and 2/17 in the Eurasian ground squirrels-sousliks and woodchucks, and disruptions of squirrel HSA 10/13 and HSA 8/4/8/12/22 syntenies in the four Spermophilus species studied here. We found that the karyotypes of Sciuridae and Leporidae are highly conserved and close to the Rodentia ancestral karyotype, while Castoridae chromosomes underwent many more changes. We suggest that Lagomorpha and Sciuridae (in contrast to all other rodent families) should be considered as core Glires lineages, characterized by cytogenetically conserved karyotypes which contain chromosomal elements inherent to karyotype of common Glires ancestor. Our data allowed us to further refine the putative ancestral karyotypes of Rodentia. We also describe here the putative ancestral karyotypes of Glires and lagomorphs. [ABSTRACT FROM AUTHOR]

Today and in the Tertiary, the geographical distribution of castorids is limited throughout all of the northern continents. Fossils of the Castoridae genus Steneofiber are abundant in many localities of Eurasia from the late Oligocene to Pliocene period. Recently, Steneofiber fossils were discovered in two localities of northern Thailand, Mae Moh and Chiang Muan coal mines, in layers of late middle Miocene age. These discoveries represent the first records of castorids from Southeast Asia and correspond to their southernmost known range. The focus of this study is to describe this new Thai species of Steneofiber and to define its wear stages from the molar occlusal surfaces by using micro-CT scan analysis. The CT scan technique permits the analysis of the virtual occlusal surface changes from wear, allowing easier comparison to related species of Steneofiber cheek teeth without destroying the teeth. The new species, Steneofiber siamensis n. sp., can be distinguished from the other species of Steneofiber by several distinct characters, longer mesostriid on p4, presence of premesostria and metastria on P4, which are smaller than most of the other known species. The occurrence of this new castorid also supports a subtropical to tropical paleoclimate for these two localities of northern Thailand. [ABSTRACT FROM AUTHOR]

Habitat selectivity by European beaver ( Castor fiber L., 1758) was studied in 226 km of river channels during their colonization of the Morava River basin (the Czech Republic), which had not been occupied by beavers for hundreds of years. The colonization started after initial reintroductions in 1991 and 1992. Annual increases in colonization of the river system from 1995 to 2007 were 15.5 ± 9.4 SD km year−1 and varied greatly between these years (min 0 km, max 33 km). Beavers appeared to be following a dispersal pattern, in which distant sites are often colonized before close-by sites. The selection of habitat variables during the colonization process varied. In the early phase of colonization, there were many areas with optimal habitat that were not occupied by beavers, and habitat selection appeared chaotic. After this early phase, the most significant habitat variable related to beaver occupation was shown to be the presence of willow ( Salix spp.) species. In the later phases, the beaver population expanded into suboptimal habitat. Settlement distance from roads, railways, and urbanized areas became less. When comparing the generalized linear models, a model from the winter of 2003/2004 had the best overall accuracy and showed excellent agreement among observed and fitted values (Cohen’s κ = 0.75). The model suggests that beavers established their home ranges at first in optimal habitat, which had not been occupied before and then subsequently in suboptimal/marginal areas. [ABSTRACT FROM AUTHOR]

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Scent marking is a common form of territorial demarcation in mammals and differential marking by the sexes may select for differences in scent gland developmental rates or size. Rates of marking reflect level of defense and so behavioral dimorphism in marking by the sexes may select for dimorphism in scent structures. Eurasian beavers (Castor fiber) are monogamous, territorial mammals that show some behavioral dimorphism in territoriality. Beavers have 2 primary scent structures, anal glands and castor sacs. Anal gland secretion appears to serve as a family or individual identifier. Castor fluid is the main source of chemical signals used for marking territories. We examined beavers collected from 3 different habitats, namely streams, creeks and tarns (small lakes), which varied in the density of beaver sites. The objectives of this study were to examine if morphological attributes of Eurasian beaver scent structures reflected differences in adult beaver territorial function or in the ontogeny of the sexes. We hypothesized that male beavers would have larger castor sacs and anal glands, and that beavers from sites of greater density, and thus greater rates of intrusion, would have larger castor sacs and anal glands. Our results showed that investment did not differ by habitat type. Although the combined weight of the scent structures did not differ between the sexes, males developed significantly larger anal glands but somewhat smaller castor sacs than females. Total investment to scent structures may be limited but allocation is flexible. Males patrol the territory more extensively and may benefit by releasing anal gland secretion to signal their identity to potential intruders. Higher rates of marking may decrease castor sac size by reducing the amount of stored scent material. Hence, even in monogamous mammals, sexual dimorphism can arise from behavioral dimorphism. [ABSTRACT FROM AUTHOR]

Periradicular bands are incremental structures seen on the external dentin surfaces of rodent incisors. They correspond to circadian developmental rhythms in dentin growth and provide a record of the growth rate of the incisor along its longitudinal axis. In the present study, we investigate the relationship between daily environmental temperatures and longitudinal growth rates of incisors in 40 Recent beavers (Castor canadensis). We also look for trends in growth rates that reflect precipitation or photoperiod. The goal is to explore the potential of using longitudinal growth data as indicators of seasonality in past environments. The sample consists of upper and lower incisors of fall-harvested beavers and upper incisors of winter-harvested beavers with known dates of death. All distances between sequential periradicular bands were measured using a dissecting microscope fitted with an ocular micrometer. All increments for each individual were matched to corresponding dates of formation. Records of daily temperatures, precipitation, and photoperiod corresponding to the locality and period of growth represented by the teeth were obtained from the National Weather Service. Time series for both dental increments and temperature were smoothed using nonparametric regression to partition “primary” (seasonal or long-term) and “secondary” (daily or short-term) signals. Upper and lower incisors differ in their primary signals in that uppers exhibit a marked decline in growth rate during the late summer and early fall, leveling off in the late fall. This trend roughly parallels seasonal decreases in temperature, precipitation, and photoperiod, although the decline in growth rate begins while the weather is still warm (in late summer). In contrast, lower incisors show only a very weak seasonal trend in growth rate. Analysis of residuals from the trend lines reveals only a weak association between daily growth rate and both daily temperature changes and precipitation. The results suggest that longitudinal growth rates in upper incisors may be used to estimate season of death in fossil rodents. [Copyright &y& Elsevier]

The systematics of the beavers (Castoridae) are reviewed and definitions are presented for each subfamilial group. Four subfamilies are recognized: primitive Agnotocastorinae (divided into two tribes, Agnotocastorini and Anchitheriomyini); burrowing beavers, Palaeocastorinae; giant beavers, Castoroidinae (containing two tribes, Castoroidini and Trogontheriini); and the Castorinae. The agnotocastorines are viewed as the ancestral group for all later subfamilies. The Palaeocastorinae is viewed as a side-branch, not ancestral or closely related to any of the later subfamilies. The Castorinae and Castoroidinae may represent a distinct clade united by dental features. [ABSTRACT FROM AUTHOR]

Here we describe a new short retroposon family of rodents. Like the primate Alu element consisting of two similar monomers, it is dimeric, but the left and right monomers are different and descend from B1 and ID short retroposons, respectively. Such elements (B1-dID) were found in the genomes of Gliridae, Sciuridae, Castoridae, Caviidae, and Hystricidae. Nucleotide sequences of this retroposon can be assigned to several structural variants. Phylogenetic analysis of B1-dID and related sequences suggests a possible scenario of B1-dID evolution in the context of rodent evolution. [ABSTRACT FROM AUTHOR]

Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene-aged deposits of the western United States and Mexico. Their postcranial remains, however, are much rarer and little studied. Yet, they offer the opportunity to investigate the locomotion of fossil gophers, shed light on the evolution of fossoriality, and enable ecomorphological comparisons with contemporaneous rodents. We present herein a quantitative study of the cranial and postcranial remains of eight different species of entoptychine gophers as well as many contemporary rodent species. We find a range of burrowing capabilities within Entoptychinae, including semifossorial scratch-digging animals and fossorial taxa with cranial adaptations to burrowing. Our results suggest the repeated evolution of chisel-tooth digging across genera. Comparisons between entoptychine gophers and contemporaneous rodent taxa show little ecomorphological overlap and suggest that the succession of burrowing rodent taxa on the landscape may have had more to do with habitat partitioning than competition., (© 2019 Wiley Periodicals, Inc.)