Skull shape and Bergmann's rule in mammals: hints from Old World porcupines

Age structure and body size of two Tibetan toad (Bufo tibetanus) populations from different elevations in China

Understanding how age and body size vary across elevations can provide insights into the evolution of life-history traits in animals. In the present study, we compared the demographic (using skeletochronology) and morphological traits of the Tibetan toad (Bufo tibetanus) between two populations from different elevational habitats (2650 vs. 3930 m). We found that (1) the mean age and body size of females were significantly greater than those of males in both populations; (2) both sexes of toads from the higher elevation tended to be significantly older in age and larger in body size; (3) there was a significant positive relationship between age and body size within each sex of the toad at both elevations; and (4) growth rates varied between the two populations, with the higher rate observed in the lower-elevation population. Our results suggested that factors other than age, such as elevation-associated temperature, influence the observed differences in body size between the two populations. Future research at a broader range of elevations should focus on these factors and evaluate their influence on animal growth patterns.

A newly discovered Hystrix primigenia specimen from the Kemiklitepe collection at Ege University Natural History Museum: insights into paleobiogeography in Eurasia

Porcupines, members of the Hystricidae family, represent a unique group of herbivorous mammals. This study details the identification of a newly discovered mandible fragment of Hystrix primigenia, along with a right cheek tooth series from the middle Turolian Kemiklitepe-A fossil locality. While Hystrix fossils are found in numerous localities, the materials are often limited to a few dental fragments or isolated teeth, posing challenges to systematic investigations. The examination of this lower tooth series prompted a comprehensive review of all H. primigenia findings across Eurasia, shedding light on its adaptive characteristics over time and space. Our paleobiogeographical analysis indicates the absence of H. depereti in Late Miocene Türkiye, while the dispersal range of H. primigenia is broader than that of H. depereti in Eurasia. Additionally, the study delves into the discussion of H. primigenia and H. depereti findings in Eurasia, ultimately refining the categorization of Late Miocene Hystrix discoveries in Türkiye to two species: H. primigenia and H. kayae. Our review suggests the possibility of an additional H. kayae finding from Samos, Greece.

Environmental and climatic drivers of phenotypic evolution and distribution changes in a widely distributed subfamily of subterranean mammals

How environmental factors shape species morphology and distributions is a key issue in ecology, especially in similar environments. Species of Myospalacinae exhibit widespread distribution spanning the eastern Eurasian steppe and the extreme adaptation to the subterranean environment, providing an excellent opportunity for investigating species responses to environmental changes. At the national scale, we here use geometric morphometric and distributional data to assess the environmental and climatic drivers of morphological evolution and distribution of Myospalacinae species in China. Based on phylogenetic relationships of Myospalacinae species constructed using genomic data in China, we integrate geometric morphometrics and ecological niche models to reveal the interspecific variation of skull morphology, trace the ancestral state, and assess factors influencing interspecific variation. Our approach further allows us to project future distributions of Myospalacinae species throughout China. We found that the interspecific morphology variations were mainly concentrated in the temporal ridge, premaxillary-frontal suture, premaxillary-maxillary suture, and molars, and the skull morphology of the two current species in Myospalacinae followed the ancestral state; temperature and precipitation were important environmental variables influencing skull morphology. Elevation, temperature annual range, and precipitation of warmest quarter were identified as dominant factors affecting the distribution of Myospalacinae species in China, and their suitable habitat area will decrease in the future. Collectively, environmental and climate changes have an effect on skull phenotypes of subterranean mammals, highlighting the contribution of phenotypic differentiation in similar environments in the formation of species phenotypes. Climate change will further shrink their habitats under future climate assumptions in the short-term. Our findings provide new insights into effects of environmental and climate change on the morphological evolution and distribution of species as well as a reference for biodiversity conservation and species management.

Body Length and Craniometrics of Non-Native Raccoons in Two Regions in Middle Japan during Early Invasion Stages

Although the genetic distribution of introduced raccoons (Procyon lotor) in recent years is well known, few studies have examined their morphometrics, especially the relationships between sex and age in the introduced populations. The aim of this study was to describe the morphological characteristics of raccoons from parts of eastern and western Japan during their early invasion stages, focusing on the relationships between body length and the principal component of craniometrics, with region, sex, age class, body length, and body mass index using a regression model. The body length increased more in males than females and in the older age class, supporting the association with intrasexual selection and competition for food resources. Positive relationships for body length and body mass index were found in craniometric analyses, particularly regarding cranial size components, in addition to age class for both sexes, while cranial size also differed between regions for females. The relationship between body length and craniometrics was inconsistent with that of subspecies originating in North America. Given the sympatric distribution of haplotypes of multiple subspecies without reproductive-isolating barriers in North America and in several introduced areas, hybridization must have occurred prior to the introduction or naturalization of this species.

Porcupines in Italian islands: update on the distribution of Hystrix cristata in Sardinia

In the last few decades, the crested porcupine (Hystrix cristata L., 1758) showed a remarkable range expansion in Italy, due to legal protection, climatic change and antropochorous releases. Particularly, porcupines have been released also in Sardinia, with first records of this large rodent in the wild dating back to 2005. Historical and social factors related to the progressive urbanization and the consequent abandonment of the traditional land use in mountain landscapes probably helped the re-expansion of forest, uncultivated fields and of animal’s species associated with these habitats. In Sardinia, a population establishment and a subsequent expansion of the area of distribution can be predicted as large portions of the island are highly suitable for the crested porcupine. Therefore, this recently introduced population should be removed to limit potential ecological and social conflicts.

Evaluation of skull and mandible morphometric measurements and three-dimensional modelling of computed tomographic images of porcupine (Hystrix cristata)

Although there have been morphological and morphometric studies on the porcupine skull, three-dimensional modelling of the skull is performed for the first time with the present study. In this study, it was aimed to model the skull and mandible of Hystrix cristata in 3D to reveal its morphometric values and the differences between the sexes. Morphometric analyses were performed on a total of eight (four male and four female) adult porcupine skulls and mandibles. Skulls and mandibles of porcupines were scanned usinf a 64-detector MDCT (General Electric Revolution) device at 80 kV, 200 MA, 639 mGY and 0.625 mm slice thickness. Skull and mandible reconstructions were made with the help of MIMICS 20.1 (Materialize) software program and the surface area and volume values of the skull and mandible were calculated. Statistical analyses were carried out using SPSS 22.0 software. The longest measurement in the skulls, based on the metric measurement points, was the total length (TL), and it was measured as 135.4750 ± 0.54976 mm in males and 134.4725 ± 0.86681 mm in females (p < 0.5). The highest value was the foramen magnum index (p < 0.5), and the lowest value the was skull index (p < 0.1). While the total volume ratio of the mandibles was 29901.64 mm3 in males, it was 27296.20 mm3 in females (p > 0.5). Statistical differences in the morphometric values of skulls and mandibles of male and female porcupines were demonstrated for the first time using CT and three-dimensional modelling software.

The Thorny Issue of African Porcupines: a New Mandible of Hystrix makapanensis from Olduvai Gorge (Tanzania) and Rediagnosis of the Species

Several porcupine taxa are reported from the middle Miocene to the early Holocene in the Old World. Among these, five species of the subfamily Hystricinae occurred in Africa approximately in the last 6 Ma: the extinct Hystrix makapanensis, Hystrix leakeyi, and Xenohystrix crassidens and the still living Hystrix africaeaustralis and Hystrix cristata. The large-sized H. makapanensis is reported from numerous sites in East and South Africa between the early Pliocene and Early Pleistocene. In this paper, we describe a new mandible of H. makapanensis from the world-renowned Tanzanian paleontological and archeological site of Olduvai Gorge (HWK West; lowermost Bed II; ca. 1.8-1.7 Ma). The discovery of the new mandible triggered a comprehensive review of the entire African record of H. makapanensis. In particular, we describe or re-analyze the samples from South Africa (Makapansgat Limeworks, Gondolin, Kromdraai, Swartkrans, and Sterkfontein), Tanzania (Olduvai and Laetoli), Ethiopia (Omo Shungura and Hadar), and Kenya (Chemeron), enriching the quantity of specimens confidently referable to this species and above all improving the information on its craniodental anatomy. On this basis, we: (1) propose an emended diagnosis of H. makapanensis; (2) point out the morphological and biometric differences between H. makapanensis and other African Hystricinae (also in terms of body mass); and (3) broaden the knowledge on the geographical and chronological distribution of this extinct species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10914-021-09588-z.

The island rule explains consistent patterns of body size evolution in terrestrial vertebrates

Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called 'island rule' provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island-mainland populations of terrestrial vertebrates. We show that 'island rule' effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.

Inter-individual behavioural variation in the crested porcupine

In this study, we investigated on the existence of personality in the crested porcupine in Central Italy by measuring variation and repeatability of three behavioural traits. Porcupines were captured through metal traps located around and in the immediate surroundings of the burrows. Then, they were manipulated and set free. Capture and handling were the experimental contexts where we measured exploration, proactivity and aggressiveness of each individual. Our results provided evidence for consistent inter-individual differences in the measured traits, with a high value of individual repeatability in aggressiveness and proactivity. The positive correlation between traits suggest the existence of a behavioural syndrome, with some individuals more aggressive and active with respect to others.

Blessing the rains down in Africa: spatiotemporal behaviour of the crested porcupine

The assessment of habitat selection and temporal patterns of activity rhythms is paramount for wildlife conservation. Studies on behavioural ecology of wild mammals are particularly challenging in tropical areas, mostly when involving rare or elusive species. Despite being a common species in Italy, the crested porcupine Hystrix cristata is threatened of extinction throughout most of its sub-Saharan range. All available information on the ecology of this species has been collected in Italy, whereas no data is present in the scientific literature on spatiotemporal behaviour of this large rodent in Africa. In this work, we attempted to determine habitat selection and temporal patterns of activity rhythms of the crested porcupine in northern Benin and neighbouring countries, through intensive camera-trapping. We collected a total of 146 records of crested porcupine, 91 in the dry season (October-March) and 55 in the rainy season (April-September). Porcupines used most habitats in proportion to their local availability, while selecting rock outcrop formations (possibly used as shelter sites) and avoiding open areas, wetlands and gallery forests. A mostly nocturnal behaviour was confirmed throughout the year, with some diurnal activity at the start and at the end of the rainy season. The importance of rains in determining birth peak has been also showed, with juvenile individuals always observed at the start and at the end of the rainy season. Full moon always inhibited activity of this large rodent, most likely evolved as an antipredatory behaviour to limit encounters with potential predators (common leopard Panthera pardus, spotted hyaena Crocuta crocuta and honey badger Mellivora capensis) and humans. Poaching pressure towards porcupines in West Africa is strong. Porcupines are killed for the traditional medicine, for their meat and because they are widely considered as a crop pest. This assessment should therefore be used as a basic tool to design conservation plans to preserve this rodent species in its native range.

Seasonal consumption of insects by the crested porcupine in Central Italy

Many herbivorous, granivorous and frugivorous rodents can integrate animal proteins in their diet, still for many of them no information is available on the importance of animal food sources. The crested porcupine, Hystrix cristata, is considered a strictly vegetarian rodent. It may integrate animal proteins through bone-gnawing, while the importance of insects in his diet is poorly known. In this study we assessed the presence of insects in the diet of this rodent in Central Italy by collecting 141 faecal samples along transects in 2016–2020. Hypogeal plant organs were the main component of the diet (absolute frequency = 50.38%; volume = 60.13%). Insects were detected only in 6.8% samples, only in February–March, at the annual birth peak for the crested porcupine. Insect consumption, although occasional, could be linked to the nutritional requirements of this rodent during lactation.

Life history and habitat do not mediate temporal changes in body size due to climate warming in rodents

Temporal changes in body size have been documented in a number of vertebrate species, with different contested drivers being suggested to explain these changes. Among these are climate warming, resource availability, competition, predation risk, human population density, island effects and others. Both life history traits (intrinsic factors such as lifespan and reproductive rate) and habitat (extrinsic factors such as vegetation type, latitude and elevation) are expected to mediate the existence of a significant temporal response of body size to climate warming but neither have been widely investigated. Using examples of rodents, we predicted that both life history traits and habitat might explain the probability of temporal response using two tests of this hypothesis. Firstly, taking advantage of new data from museum collections spanning the last 106 years, we investigated geographical and temporal variation in cranial size (a proxy for body size) in six African rodent species of two murid subfamilies (Murinae and Gerbillinae) of varying life history, degree of commensality, range size, and habitat. Two species, the commensal Mastomys natalensis, and the non-commensal Otomys unisulcatus showed significant temporal changes in body size, with the former increasing and the latter decreasing, in relation with climate warming. Commensalism could explain the increase in size with time due to steadily increasing food availability through increased agricultural production. Apart from this, we found no general life history or habitat predictors of a temporal response in African rodents. Secondly, in order to further test this hypothesis, we incorporated our data into a meta-analysis based on published literature on temporal responses in rodents, resulting in a combined dataset for 50 species from seven families worldwide; among these, 29 species showed no significant change, eight showed a significant increase in size, and 13 showed a decline in size. Using a binomial logistic regression model for these metadata, we found that none of our chosen life history or habitat predictors could significantly explain the probability of a temporal response to climate warming, reinforcing our conclusion based on the more detailed data from the six African species.

Habitat productivity is a poor predictor of body size in rodents

The “resource availability hypothesis” predicts occurrence of larger rodents in more productive habitats. This prediction was tested in a dataset of 1,301 rodent species. We used adult body mass as a measure of body size and normalized difference vegetation index (NDVI) as a measure of habitat productivity. We utilized a cross-species approach to investigate the association between these variables. This was done at both the order level (Rodentia) and at narrower taxonomic scales. We applied phylogenetic generalized least squares (PGLS) to correct for phylogenetic relationships. The relationship between body mas and NDVI was also investigated across rodent assemblages. We controlled for spatial autocorrelation using generalized least squares (GLS) analysis. The cross-species approach found extremely low support for the resource availability hypothesis. This was reflected by a weak positive association between body mass and NDVI at the order level. We find a positive association in only a minority of rodent subtaxa. The best fit GLS model detected no significant association between body mass and NDVI across assemblages. Thus, our results do not support the view that resource availability plays a major role in explaining geographic variation in rodent body size.

Interspecific Aggressions between Crested Porcupines and Roe Deer

Despite being common amongst carnivore mammals, behavioral interference between wild herbivore species is poorly documented. Particularly, in temperate areas, where the ungulate guild is composed of a few species, and large-sized rodents are scarce, most cases of interspecific interactions involve at least one alien species. In this work, we report the first data on behavioral interactions between roe deer, Capreolus capreolus, and crested porcupine, Hystrix cristata. Aggressions by crested porcupines toward roe deer were observed in 34 out of 202 observations of both species feeding at the same site. In the other 168 observations, roe deer and porcupines shared the same feeding area, without any interaction. In 58% cases of interaction, porcupines chased and pushed roe deer away from feeding areas, and in several other cases, roe deer were bitten, or injured with quills. Aggressions by porcupines occurred mostly during warm months, when roe deer are mostly solitary and when competition for food between these species is suggested to be the highest, and against single female individuals.