Alien war: ectoparasite load, diet and temporal niche partitioning in a multi-species assembly of small rodents

The ratting of North America: A 350-year retrospective on Rattus species compositions and competition

While the impacts of black (Rattus rattus) and brown (Rattus norvegicus) rats on human society are well documented-including the spread of disease, broad-scale environmental destruction, and billions spent annually on animal control-little is known about their ecology and behavior in urban areas due to the challenges of studying animals in city environments. We use isotopic and ZooMS analysis of archaeological (1550s-1900 CE) rat remains from eastern North America to provide a large-scale framework for species arrival, interspecific competition, and dietary ecology. Brown rats arrived earlier than expected and rapidly outcompeted black rats in coastal urban areas. This replacement happened despite evidence that the two species occupy different trophic positions. Findings include the earliest molecularly confirmed brown rat in the Americas and show a deep ecological structure to how rats exploit human-structured areas, with implications for understanding urban zoonosis, rat management, and ecosystem planning as well as broader themes of rat dispersal, phylogeny, evolutionary ecology, and climate impacts.

Critical thermal limits and temperature-dependent walking speed may mediate coexistence between the native winter ant (Prenolepis imparis) and the invasive Argentine ant (Linepithemahumile)

Comparing the thermal tolerance and performance of native and invasive species from varying climatic origins may explain why some native and invasive species can coexist. We compared the thermal niches of an invasive and native ant species. The Argentine ant (Linepithema humile) is an invasive species that has spread to Mediterranean climates worldwide, where it is associated with losses in native arthropod biodiversity. In northern California, long-term surveys of ant biodiversity have shown that the winter ant (Prenolepis imparis) is the native species best able to coexist with Argentine ants. Both species tend hemipteran scales for food, and previous research suggests that these species' coexistence may depend on seasonal partitioning: winter ants are active primarily in the colder winter months, while Argentine ants are active primarily in the warmer months in northern California. We investigated the physiological basis of seasonal partitioning in Argentine and winter ants by a) measuring critical thermal limits, and b) comparing how ant walking speed varies with temperature. While both species had similar CTmax values, we found differences between the two species' critical thermal minima that may allow winter ants to remain functional at ecologically relevant temperatures between 0 and 2.5 °C. We also found that winter ants' walking speeds are significantly less temperature-dependent than those of Argentine ants. Winter ants walk faster than Argentine ants at low temperatures, which may allow the winter ants to remain active and forage at lower winter temperatures. These results suggest that partitioning based on differences in temperature tolerance promotes the winter ant's continued occupation of areas invaded by the Argentine ant.

Activity patterns and interactions of rodents in an assemblage composed by native species and the introduced black rat: implications for pathogen transmission

Background

The degree of temporal overlap between sympatric wild hosts species and their behavioral interactions can be highly relevant to the transmission of pathogens. However, this topic has been scantly addressed. Furthermore, temporal overlap and interactions within an assemblage of wild rodents composed of native and introduced species have been rarely discussed worldwide. We assessed the nocturnal activity patterns and interactions between rodent taxa of an assemblage consisting of native species (Oligoryzomys longicaudatus, Abrothrix hirta, and Abrothrix olivaceus) and the introduced black rat (Rattus rattus) in a temperate forest from southern Chile. All rodent species in this study are known hosts for various zoonotic pathogens.

Results

We found a high nocturnal temporal overlap within the rodent assemblage. However, pairwise comparisons of temporal activity patterns indicated significant differences among all taxa. Rattus rattus showed aggressive behaviors against all native rodents more frequently than against their conspecifics. As for native rodents, agonistic behaviors were the most common interactions between individuals of the same taxon and between individuals of different taxa (O. longicaudatus vs Abrothrix spp.).

Conclusions

Our findings reveal several interactions among rodent taxa that may have implications for pathogens such as hantaviruses, Leptospira spp., and vector-borne pathogens. Furthermore, their transmission may be facilitated by the temporal overlap observed between rodent taxa.

Camera traps reveal overlap and seasonal variation in the diel activity of arboreal and semi-arboreal mammals

Our study aimed to investigate seasonal variation in the activity of arboreal and semi-arboreal mammals and investigate their overlap in temporal activity, as well temporal shifts in activity because of behavioural interference. In our camera trapping study in a fragmented landscape in south-eastern Australia, a total of ten arboreal and semi-arboreal species were found, with 35,671 independent observations recorded over 6517 camera trap nights. All species were found to be nocturnal; however, a notable number of daytime observations were made for several species (i.e. brown antechinus, Antechinus stuartii; sugar glider, Petaurus breviceps; bush rat, Rattus fuscipes; brown rat, Rattus norvegicus). Seasonal variations in diel activity were observed through an increase in crepuscular activity in spring and summer for antechinus, sugar gliders, brown rats, brushtail possums, Trichosurus vulpecula and ringtail possums, Pseudocheirus peregrinus. Diel activity overlap between species was high, that is 26/28 species comparisons had overlap coefficients (Δ) > 0.75. The species pair with the least amount of overlap was between southern bobucks, Trichosurus cunninghami and brown antechinus (Δ4 = 0.66). The species pair with the most overlap was between the native sugar glider and introduced brown rat (Δ4 = 0.93). When comparing the activity of sugar gliders in sites with low and high abundance of brown rats, sugar gliders appear to shift their activity relative to the brown rats. Similarly, behavioural interference was also observed between antechinus and sugar gliders, and when comparing sites of low and high abundance of sugar glider, antechinus had a shift in activity. Our work provides some of the first quantification of temporal patterns for several of the species in this study, and the first for a community of arboreal and semi-arboreal mammals. Our results indicate that some shifts in behaviour are potentially occurring in response to behavioural interference, allowing for coexistence by means of temporal partitioning.

Temporal Partitioning between Forest-Dwelling Small Rodents in a Mediterranean Deciduous Woodland

Temporal partitioning is reported as one of the main strategies adopted by coexisting mammal species to limit interspecific competition and behavioural interference. In the last decades, camera-trapping surveys have provided valuable insights in assessing temporal niche and activity rhythms of medium and large-sized mammalian species. Conversely, this method has been poorly applied to small rodents. In this work we aimed at assessing temporal niche partitioning between two species of forest-dwelling small rodents—Apodemus flavicollis and Clethrionomys glareolus—by means of intensive camera-trapping. Camera traps were placed in areas where previous genetic analyses have confirmed the only presence of A. flavicollis amongst wood mice species, to prevent misinterpretation of records. We collected 124 independent records of A. flavicollis and 67 records of C. glareolus over three years. The former was mostly nocturnal, with activity peaking after midnight, whereas the latter was mostly active at dawn and dusk. Therefore, a limited temporal overlap was observed, confirming the potential for interspecific competition. Intraguild interference competition between A. flavicollis and C. glareolus may play a pivotal role forcing C. glareolus to be more active in daylight hours where, the more strictly nocturnal A. flavicollis is present. Nocturnal activity of C. glareolus was limited and not influenced by moon phases, whereas A. flavicollis was mostly active in the darkest nights, avoiding bright moonlight nights.

Isotopic Niche of Syntopic Granivores in Commercial Orchards and Meadows

Simple Summary

Granivorous murids, namely striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice, occur in a variety of habitats and live syntopically in agricultural areas. Agroecosystems may be quite complex isotopically with δ¹⁵N values being influenced by many internal and external fluxes. Using isotopic (δ¹⁵N and δ¹³C) compositions from hair samples, we analysed isotopic niches of granivores in apple and plum orchards, raspberry and currant plantations, and nearby meadows in Lithuania. As the main hypothesis, we expected differences in the isotopic niches of these species (being a proxy for their diet), minimising interspecific competition. Striped field and yellow-necked mice were trapped in every habitat. Therefore, syntopic co-occurrence of granivores depended on the presence of harvest mice in the apple orchards, raspberry plantations, and meadows that served as control habitats. All species were fully separated according to δ¹⁵N values, presuming different amounts of food of animal origin in their diet. The separation of species according to δ¹³C was not expressed in all habitats. The core dietary niches of these species were fully separated in the apple orchards and raspberry plantations. Intraspecific differences of the isotopic niche were not present in any of the three species: that is, resources were equally used by males and females, adults, subadults, and juveniles.

Abstract

In agricultural habitats, diets and trophic positions of syntopic granivorous small mammals are not known sufficiently. Agroecosystems may be quite complex isotopically and the most complex situation concerns the nitrogen-15 isotope as δ¹⁵N values are influenced by many internal and external fluxes. We analysed the isotopic niches of striped field (Apodemus agrarius), yellow-necked (Apodemus flavicollis), and harvest (Micromys minutus) mice living sympatrically and syntopically in apple and plum orchards, raspberry and currant plantations, and nearby meadows that were used as control habitats. Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios from hair samples were used as a proxy for their diet. As the main hypothesis, we expected differences in the isotopic niches of these three species, minimising interspecific competition. All species were fully separated according to δ¹⁵N values, presuming different amounts of food of animal origin in their diet. The separation of species according to δ¹³C was not expressed in all habitats. The core dietary niches of these species were fully separated in the apple orchards and raspberry plantations. Intraspecific differences of the isotopic niche were not present in any of the three species: that is, resources were equally used by males and females, adults, subadults, and juveniles.

Hostile Interactions of Punjab Urial (Ovis vignei punjabiensis) towards Indian Gazelle (Gazella bennettii) during Feeding Sessions in Captive Breeding Settings

Simple Summary

Multiple factors, both natural and anthropogenic, are driving most of the wild species to the verge of extinction across the globe. In order to conserve these threatened species, various conservation interventions and strategies are adopted, among which is re-introduction of captive stocks of species into the wild habitats where they vanished from. Captive breeding is one of the promising tools for endangered species preservation. Providing social enrichment to the captive stocks is an important step in the management, in particular for stocks, which are aimed for re-introduction. The subject species of this study, i.e., Punjab urial (Ovis vignei punjabiensis) and Indian gazelle (Gazella bennettii) are being reared in captivity with the aim of re-introduction. As there is scarcity of information regarding the behavioral aspects of captive species, especially ungulates, this study aimed at understanding the dynamics of their interactions. The current study reported that Punjab urial, being the dominant species, exerts itself on the submissive and subordinate species, the Indian gazelle. This negative interference can possibly lead to negative ramifications in the form of stress and injuries in the short term, while negative effects on population growth in the long term. Thus, this study recommends separate rearing of these species to eliminate the hazardous competition between them.

Abstract

Natural wildlife habitats are regularly subjected to anthropogenic pressures for different purposes, which are heading the biodiversity towards drastic decline. Several endangered wild species are raised in captivity with the aim of re-introduction. In some instances, mixed herds’ rearing approach in captivity is adopted for providing social enrichment to captive stocks; however, the impacts of species on each other are least documented. We tested our prediction that keeping mixed herds of captive wild sheep and antelopes provides adequate social enrichment to the captive stocks: if interspecific interactions are balanced. In the current study, we studied the interspecific competition between mixed herds of captive Punjab urial (Ovis vignei punjabiensis) and Indian gazelle (Gazella bennettii) at Manglot Wildlife Park, Nowshera District, Khyber Pakhtunkhwa Province, Pakistan. We documented the negative effects of behavioural interference by Punjab urial on the feeding behaviour of Indian gazelle. The outcome of the current study revealed that Punjab urial are highly intolerant towards Indian gazelle, with high interference during feeding. Out of the total aggressive events, 77% (N = 1259) of events ended up with win/loss, in which Punjab urial dominated the Indian gazelle 3.5 times. Moreover, lopsided dominance by Punjab urial resulted in increased intraspecific competition among Indian gazelle (p < 0.001). Current study divulged Indian gazelle to be the subordinate species, with less intake of food. Instead of providing social enrichment by heterospecifics, the Punjab urial is negatively affecting the Indian gazelle, therefore, the results of our study discourage the practice of admix captive breeding for wild sheep and antelopes.

Spatiotemporal Overlap between the European Brown Hare and Its Potential Predators and Competitors

Analysis of spatiotemporal partitioning is pivotal to shed light on interspecific coexistence. Most research effort has involved large-sized carnivores and their prey, whereas little attention has been devoted to lagomorphs. We assessed spatiotemporal overlap among the European brown hare Lepus europaeus and its potential competitors and predators through camera-trapping in an area in Central Italy. We estimated the interspecific patterns of the spatiotemporal activity rhythms of brown hares, its potential predators (the red fox Vulpes vulpes, the pine marten Martes martes, the domestic cat Felis catus, and the domestic dog Canis familiaris), and a competitor, the roe deer Capreolus capreolus. Brown hare activity was studied in natural conditions as well as in a fenced area that excluded terrestrial predators and competitors. Free-ranging hares developed a more nocturnal behavior to avoid diurnal predators (i.e., domestic carnivores and martens). Although high temporal overlap was observed between free-ranging brown hares and both red foxes (82%) and roe deer (81%), hares avoided fox by being more active on darkest nights, as well as avoided roe deer through spatial partitioning. We suggest that hares may adapt their spatiotemporal behavior to avoid potential predators and competitors.

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.

Frequency of Occurrence and Ingested Biomass of Different Prey of the Barn Owl Tyto alba in an Island Ecosystem

The Barn Owl Tyto alba is commonly reported as a non-selective predator of small mammals, and its diet has been thoroughly analyzed also to assess the small mammal assembly composition in many study areas. The aim of this work was to analyze the diet of the Barn Owl in the Elba island through the analysis of 161 pellets collected in September 2020. Undigested fragments were isolated and compared with reference collections. We confirmed that the Barn Owl is a typical predator of field mice (62% of relative frequency), with synanthropic murid rodents as the second category of prey. The frequency of consumption of shrews increased by 9% with respect to the previous work, suggesting that the natural environment of Elba island is still in a good health status. Moreover, fragments of two newborn hares were detected, increasing the knowledge on the local trophic spectrum of the Barn Owl. Finally, the skull of a Geoffroy’s Myotis Myotis emarginatus confirmed the presence of this species in Elba island after over 60 years from the first unconfirmed record. Repeated studies conducted in the same study site may provide useful information on prey population trends and local environmental status.

Competitor densities, habitat, and weather: effects on interspecific interactions between wild deer species

There is a growing interest on the potential interplay between weather, habitat, and interspecific competition on population dynamics of wild herbivores. Favorable environmental conditions may buffer the negative effects of competition; conversely, competition may be expected to be stronger under harsh environmental conditions. We investigated relationships between competitor abundance, weather, and habitat cover on density and local distribution of a medium‐sized herbivore, the roe deer Capreolus capreolus, as well as its spatial overlap with fallow deer Dama dama in a Mediterranean protected area. Over 11 years (2007–2017), roe deer density was not affected by spring–summer rainfall in the previous year and decreased with increasing density of fallow deer in the previous year. Hence, over the considered temporal scale, results supported a major role of competition over weather in influencing population trends of roe deer. At a finer spatial scale, roe deer occupancy was negatively affected by local abundance of fallow deer, especially in “poorer” habitats. We found a slight support for a positive effect of fallow deer density on interspecific spatial overlap. Moreover, fine‐scale spatial overlap between deer species increased with decreasing rainfall in spring–summer. Fallow deer were introduced to our study area in historical times and their role as superior competitors over roe deer has been found also in other study areas. We suggest a potential role of harsh weather conditions during the growing season of vegetation (i.e. scarce rainfall) in triggering the potential for ecological overlap, emphasizing the negative effects of interspecific competition.

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.