Black Rats Rattus Research Articles

First mtDNA Sequences and Body Measurements for Rattus norvegicus from the Mediterranean Island of Cyprus

Invasive species are the primary driver of island taxa extinctions and, among them, those belonging to the genus Rattus are considered as the most damaging. The presence of black rat (Rattus rattus) on Cyprus has long been established, while that of brown rat (Rattus norvegicus) is dubious. This study is the first to provide molecular and morphological data to document the occurrence of R. norvegicus in the island of Cyprus. A total of 223 black rats and 14 brown rats were collected. Each sample was first taxonomically attributed on the basis of body measurements and cranial observations. Four of the specimens identified as R. norvegicus and one identified as R. rattus were subjected to molecular characterization in order to corroborate species identification. The analyses of the mitochondrial control region were consistent with morphological data, supporting the taxonomic identification of the samples. At least two maternal molecular lineages for R. norvegicus were found in Cyprus. The small number of brown rats collected in the island, as well as the large number of samples of black rats retrieved in the past years might be an indication that the distribution of R. norvegicus is still limited into three out of the six districts of Cyprus.

Seasonal demography of different black rat (Rattus rattus) populations under contrasting natural habitats in Guadeloupe (Lesser Antilles, Caribbean)

The black rat (Rattus rattus) is one of the most widespread rodents on islands worldwide, introduced over the last five centuries. However, reliable information concerning how biotic or abiotic factors influence key parameters of black rat population biology in insular contexts is currently unavailable. Here we aim to document the relative abundance of rat populations and evaluate how the age structure and the body mass of adult individual vary seasonally in different forest environments under contrasting climatic conditions. Rats were captured during wet and dry seasons in 2017–2018 at one or two sites in each of the four natural forested environments of Guadeloupe, all of which experience widely different annual rainfall (semi-deciduous dry forest, seasonal evergreen forest, mountain rainforest and Pterocarpus officinalis swamp forest). A total of 171 black rats were captured during a 1018 trap-night effort. Overall capture results confirm this species to thrive in all the natural forested environments we investigated. With the exception of the P. officinalis swamp forest, black rat populations reach higher relative abundances during the wet season due to juvenile and sub-adult recruitment at the end of the dry season. In contrast, in the P. officinalis swamp forest, breeding activity continues during both seasons and relative rat abundance appears to fluctuate less seasonally. The relative abundance of adult black rats is also higher in the seasonal semi-evergreen and rainforests that experience little or no water stress. These contexts therefore appear the most favourable for sustaining black rat populations, a pattern that is most likely connected to a combination of climatic and/or edaphic parameters that condition the year-round availability and abundance of food resources.

Seabirds blinded by ticks

In December 2017, on Possession Island (part of the Crozet Archipelago in the southern Indian Ocean), we observed two breeding white‐chinned petrels (Procellaria aequinoctialis ) with very high levels of tick (Ixodes kerguelenensis ) infestation on both eyes. This degree of infestation was likely responsible for the birds’ death. Although this rare observation may seem anecdotal, it reveals that ticks can be fatal for a long‐lived colonial seabird species, in this case one that is already under pressure from fisheries bycatch and predation by introduced black rats (Rattus rattus ). It also raises questions about the frequency and spatial distribution of such a phenomenon and the conditions that may have been responsible for its occurrence. Such high parasite loads imply high local tick abundances but also a lack of preening by the partner. Could this be linked to the recent death of the partner? Infestations by ticks can affect the health of hosts through blood loss, the injection of toxins, and the transmission of infectious agents. In this instance, the mechanical blocking of eyesight may also have affected the birds’ behavior. The potential impact of climate change on local parasitic infestation levels is another important question. Parasites and diseases can harm endangered species in polar and subpolar areas, and could play critical roles in some circumstances.

Risk-taking behavior of bull-headed shrikes that recently colonized islands

Individuals which have invaded urbanized environments are reported to engage in riskier behaviors, possibly influenced by the scarcity of predators in urbanized areas. Here, we studied the risk-taking behavior of birds which had invaded a new natural environment, rather than an artificial urban environment, using recently established populations of the bull-headed shrike Lanius bucephalus, which naturally colonized three subtropical islands in Japan. We compared flight initiation distance (FID), the distance at which an individual approached by a human initiates flight, between the islands and the temperate mainland. FID was longer for the insular shrikes compared with the mainland shrikes after controlling for other factors, indicating that the individuals which had invaded a new natural environment had a lower propensity for risk-taking. A possible explanation for these results is that low risk-taking behavior might be adaptive on the islands due to predation by the black rat Rattus rattus, an unfamiliar predator not found in shrike habitats on the temperate mainland. Further studies are needed to examine the nest predation rate, predator species, and nest site selection of these insular shrike populations.

Rats and prions at Tristan da Cunha Island

Tristan da Cunha is a 96 km2 volcanic island in the South Atlantic Ocean. Black Rats Rattus rattus reached the island from a shipwreck in 1882 and their depredation of seabirds’ eggs and chicks are likely partly responsible for the much lower densities of burrow-nesting petrels, compared with adjacent rodent-free islands in the archipelago. We monitored a colony of Broad-billed Prions Pachyptila vittata breeding in a coastal cliff cave in 2015/2016, where a maximum of 6% of chicks survived from 310 nests. We suspect rats frequently depredated eggs (36% of eggs were found broken with rat bite marks) and infrared trail cameras recorded how rats repeatedly hassled chicks, although no direct chick depredations were recorded.

Genetic diversity and origins of invasive black rats (Rattus rattus) in Benin, West Africa

Black rats (Rattus rattus) are native to the Indian subcontinent but have now colonized most continents and islands following human movements and international trade. They are involved in the circulation and transmission to humans of many zoonotic agents as well as in massive damage to food stocks and native biodiversity in the regions they have settled. This study investigates the genetic diversity and possible origins of black rats from Benin, West Africa. We sequenced the complete mitochondrial cytochrome b gene in 90 individuals from nine localities in Benin. These sequences were subsequently compared to 390 other cytochrome b haplotypes from individuals from various European, Asian, American and African localities. Nucleotide polymorphism analysis, haplotype network and maximum likelihood phylogenetic tree reconstructions showed low mitochondrial diversity in black rats from Benin. Our results also suggest at least two distinct introduction events: one introduction probably occurred during the spice trade (15th-17th century) through the Indies Road connecting Europe to Asia. Other introduction events could have occurred more recently following the intensification of globalized trade from the eighteenth century, and onwards.

Rats as potential reservoirs for neglected zoonotic Bartonella species in Flanders, Belgium

BackgroundBartonella spp. are vector-borne pathogens transmitted to humans via blood-sucking arthropods. Rodents such as the black rat (Rattus rattus) and Norway rat (R. norvegicus) are thought to be the main reservoirs. An infection with rodent-associated Bartonella spp. may cause severe symptoms in humans such as endocarditis and neuroretinitis. The current knowledge of Bartonella prevalence in rats from western Europe is scarce.MethodsRats and a few other rodent by-catches were trapped in the context of a rodenticide resistance study at different sites in Flanders, Belgium. During dissection, biometric data were collected, and spleen tissues were taken. DNA was extracted from spleen samples and tested for Bartonella spp. by conventional generic polymerase chain reaction (PCR). To determine the Bartonella species, a selected number of amplicons were sequenced and compared with GenBank entries.ResultsIn total, 1123 rodents were trapped. The predominate species was R. norvegicus (99.64%). Other rodents trapped included: two water voles (Arvicola amphibius, 0.18%); one colour rat (R. norvegicus forma domestica, 0.09%); and one muskrat (Ondatra zibethicus, 0.09%). PCR analysis of 1097 rodents resulted in 410 (37.37%, 95% CI: 34.50–40.31%) Bartonella spp. DNA-positive samples. Bartonella tribocorum (94.68%, 95% CI: 88.02–98.25%) was the most frequently detected Bartonella species, followed by B. grahamii (3.19%, 95% CI: 0.66–9.04%) and B. doshiae (1.06%, 95% CI: 0.03–5.79%). An uncultured Bartonella species occurred in one water vole (1.06%, 95% CI: 0.03–5.79%). There was a significantly higher Bartonella prevalence in older rats compared to juveniles and a significant difference in Bartonella prevalence concerning the localisation of trapping sites. In contrast, there was no statistically significant difference in Bartonella prevalence regarding sex, degree of urbanisation and season.ConclusionsBased on the high prevalence found, we conclude that the Norway rat seems to be a key reservoir host for zoonotic B. tribocorum in Belgium.

Molecular identification of the Trypanosoma (Herpetosoma) lewisi clade in black rats (Rattus rattus) from Australia.

Invasive rodent species are known hosts for a diverse range of infectious microorganisms and have long been associated with the spread of disease globally. The present study describes molecular evidence for the presence of a Trypanosoma sp. from black rats (Rattus rattus) in northern Sydney, Australia. Sequences of the 18S ribosomal RNA (rRNA) locus were obtained in two out of eleven (18%) blood samples with subsequent phylogenetic analysis confirming the identity within the Trypanosoma lewisi clade.

A review of mammal eradications on Mediterranean islands

Abstract Impacts of alien invasive species on island communities and ecosystems may be even more detrimental than on the mainland. Therefore, since the 1950s, hundreds of restoration projects have been implemented worldwide, with the aim of controlling or eradicating alien species from islands. To date, no review has been focused on eradication on Mediterranean islands. To fill the gap, I reviewed the available information concerning mammal eradications so far carried out on Mediterranean islands, examining the details of several aspects of project implementation and monitoring. I obtained data for 139 attempted eradications on 107 Mediterranean islands in eight countries, with Greece, Italy, and Spain accounting for the highest number. Eradication projects targeted 13 mammal species. The black rat Rattus rattus was the target of over 75% of the known attempted eradications in the Mediterranean Basin; other species targeted were feral goat Capra hircus, house mouse Mus musculus, European rabbit Oryctolagus cuniculus, and domestic cat Felis catus. The most widely adopted technique was poisoning (77% of all eradications), followed by trapping (15%) and hunting (4%). However, techniques were largely target‐specific. The average failure rate was about 11%. However, this percentage varied according to the specific mammalian order, and eradications of Carnivora failed more often than those of other mammals. Among rodents, house mouse eradication attained a very high failure rate (75%). Reinvasion occurred after 15% of successful eradications. A better understanding of the motivations of animal rights activists may improve the chance of success when eradicating charismatic or domesticated species. Furthermore, it is crucial to collect data and case studies about reinvasions, in order to strengthen biosecurity programmes following eradication. As in other parts of the world, the next frontier in alien mammal management on Mediterranean islands concerns the eradication of invasive species from inhabited islands.

Invasive rat establishment and changes in small mammal populations on Caribbean Islands following two hurricanes

Invasive mammals, particularly black rats (Rattus rattus), house mice (Mus musculus), and mongoose (Herpestes auropunctatus) are established on many tropical islands and threaten natural resources such as native birds, sea turtles, lizards, invertebrates, and plants. St. Croix (U.S. Virgin Islands, Caribbean) has a diversity of natural resources being protected from invasive mammals by U.S. conservation agencies. Sandy Point National Wildlife Refuge and Buck Island Reef National Monument receive among the highest density of nesting sea turtles in the region, including annual nesting populations of 50–250 leatherbacks (Dermochelys coriacea), 25–80 hawksbills (Eretmochelys imbricata), and 100–250 green turtles (Chelonia mydas). Buck Island Reef National Monument and Green Cay National Wildlife Refuge are small islands near St. Croix Island that have endangered St. Croix ground lizards (Ameiva polops) established. Rodents and mongoose threaten each of these natural resources. The goal of our study was to determine the types of small mammals (i.e., mongoose, rats, and/or house mice) that are established in each of the three hotspot locations mentioned, and to determine how two severe hurricanes (Irma and Maria) affected the small mammal populations. We used traps and tracking tunnels, which are baited ink cards placed in tunnels so that animal foot prints can be identified, to determine presence and relative abundances of small mammal species. We found that: 1) black rats invaded and established, possibly by rafting and/or swimming, Green Cay following the hurricanes, 2) house mice, rats, and mongoose were present before and after the hurricanes at Sandy Point (mice had not been documented prior to our sampling), and house mouse abundance significantly increased (>2.5 times pre-hurricane levels) 9-months after the hurricanes, and 3) the house mouse population more than doubled 15-months after the hurricanes on Buck Island. Land and resource managers benefit from knowing the composition and relative abundances of the small mammal communities, and the presence of house mice will make predator-free management efforts challenging. Surveillance using tracking tunnels enables rapid confirmation of new invasive species in isolated habitats and following large storms, as demonstrated by our finding that black rats established on Green Cay following the 2017 hurricanes.

Managing the Effects of Introduced Predators on Hawaiian Endangered Seabirds

ABSTRACTIntroduced predators are one of the greatest threats facing seabirds worldwide. We investigated the effects of multiple introduced predators on 2 endangered seabirds, the Newell's shearwater (Puffinus newelli) and the Hawaiian petrel (Pterodroma sandwichensis), on the island of Kauaʻi, Hawaiʻi, USA. Between 2011 and 2017, we recorded 309 depredations of which 35.6% were by feral cats, 50.2% by black rats (Rattus rattus), 10.4% by pigs (Sus scrofa; feral pigs), and 3.9% by barn owls (Tyto alba). Cats were the most destructive of the predators because they killed more breeding adults than chicks, which had repercussions on breeding probability in following years. Cats and rats were also the most prevalent of all the predators, depredating birds at all of the sites under consideration regardless of how remote or inaccessible. We also considered the effectiveness of predator control over the study period. Reproductive success at all sites increased once predator control operations were in place and depredations by all species except barn owls decreased. Furthermore, we modeled population trajectories for all sites with and without predator control. Without predator control, population trajectories at all sites declined rapidly over 50 years. With predator control operations in place, populations at all sites increased; thus, controlling introduced predators at endangered seabird colonies is important for their management. © 2020 The Wildlife Society.

Population recovery of alien black rats Rattus rattus: A test of reinvasion theory

AbstractReinvasion of pest animals after incomplete control is a major challenge for invasive species management, yet little is known about the behavioural and demographic categories of reinvaders or the mechanisms that drive population‐level responses to control. To understand the fine‐scale mechanisms of reinvasion, we examined changes in demography, movements and activity patterns of reinvading alien black rats Rattus rattus in the short (4 weeks) and longer term (3 months) following localised experimental pest removal. Using recovery and invasion theory, we tested three hypothesised mechanisms of reinvasion: the ‘in situ effect’, the ‘trickle effect’ and the ‘vacuum effect’. We created space for reinvasion by removing black rats from the core of replicate 1‐ha plots (short‐term experiment) and later by removing animals from the entire plot (longer‐term experiment). Reinvaders were characterised as dispersing juveniles, floaters or neighbours. Radio‐tracking quantified home range changes for adjacent resident animals (short‐term experiment only). In the short term, there was no net influx of rats after targeted removal. Radio‐tracked residents’ movements were highly variable and displayed no directional changes after nearby conspecifics were removed. However, in the longer term, removal led to slow population recovery through a mix of reinvading floaters, dispersing juveniles and shifting residents. These responses best support a hypothesis of reinvasion through a trickle effect, with rats being extremely mobile and having a high degree of population turnover, even in untreated sites. Our findings provide the first test of reinvasion theory at a small scale, demonstrating the importance of understanding the differing categories of reinvaders and mechanisms of reinvasion after population control. These mechanisms drive the rate of population recovery and, in turn, should help determine which strategy of pest control should be used, and the frequency with which they are implemented, in order to slow the recovery of pest populations.

Leishmaniasis in Saudi Arabia: Current situation and future perspectives.

Background and Objective:Leishmaniasis is endemic in Saudi Arabia with cases reported in many regions. This review refers to publications on leishmaniasis in Saudi Arabia and discusses issues related to parasite species, clinical manifestation and diagnosis.Methods:This research was done at Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia by systematic literature search on PubMed and Google Scholar databases from 1989 to 2018. Selection criteria included original articles reporting on visceral leishmaniasis (VL) or cutaneous leishmaniasis (CL) in Saudi Arabia.Results:The search identified 16 eligible articles, six for VL and 10 for CL. VL was reported in areas known to be non-endemic. Leishmania donovani was the main cause for human VL while Leishmania infantum seemed to cause the disease in animals. Dogs were considered the main reservoir hosts and black rats (Rattus rattus) were potential hosts. VL mainly affected infants and young children. It is important to note that VL diagnosis was based on either invasive parasite detection procedures or serologically using indirect hemagglutination test. CL represented the most frequent clinical form with the main endemic foci reported in the South-West and Eastern regions. CL appeared to have no demographic or socioeconomic restriction; it affected both rural and urban citizens, with the majority occurring among farmers. Travelling was recognized as an important risk factor. Leishmania tropica and Leishmania major were recognized as the main causes for CL.Conclusion:This report summarizes the potential risks for VL and CL in Saudi Arabia in areas known to be non-endemic. There are substantial gaps in knowledge and practices in regard to leishmaniasis in Saudi Arabia, highlighting the need for more research and medical surveillance targeting the disease in humans and animals.

Effects of the Black Rat (Rattus rattus) on Tropical Islands: Helpful or Harmful?

Rats do not enjoy a particularly good reputation, especially in regards to the environment. Many know rats to be pests, spreaders of diseases, and overall ruinous to the environments they are introduced to.The focus of this poster is on the impact of black rats (Rattus rattus) and brown rats (Rattus norvegicus) on tropical islands. Many studies support the idea that introduced rats destroy the ecosystems of tropical islands by negatively impacting the islands' bird populations. However, a study suggested that rats might have a positive impact on tropical islands through spreading seeds of different plants across the terrain. However, after the compilation and analysis of several studies regarding rats' impacts on tropical islands, it was concluded that the negative impact of rats on tropical islands outweigh the positive impacts.

Some vertebrate prey of Barn Owls Tyto alba sumbaensis on Sumba and Rote, Indonesia

The diet of the Barn Owl Tyto alba sumbaensis is little known in Wallacea. Samples of pellets from nests in a church in an urban setting on Sumba and in a forested, limestone cliff setting near Nembrala (Nemberala) on the small island of Rote (Roti), off Timor, were collected in July 2001 and July 2002, respectively. The Sumba sample contained the remains of rodents (three Black Rats Rattus rattus , four Pacific Rats R. exulans and one probable House Mouse Mus musculus ) and birds (17 Eurasian Tree Sparrows Passer montanus ). The sample from Rote contained the remains of 30 small fruit-bats (24 Geoffroy’s Rousettes Rousettus amplexicaudatus and six that were probably also this species).

Black Rats eradicated from Big Green Island in Bass Strait, Tasmania

Big Green Island is a 129-ha Nature Reserve and part of the Furneaux Group of islands in Bass Strait, southeastern Australia. Beginning in April 2016, Black Rats Rattus rattus were targeted for eradication using poisoning with 50 ppm brodifacoum wax blocks via a 25 x 25 m grid of bait stations (16 stations per ha) checked daily for a four-week period followed by three one-week visits over an eight-week period. After six weeks, rodent chew-cards were deployed exposing pockets of rat activity on the island. Island-wide monitoring led to the capture of six rats, the last known rat being killed in November 2016. Monitoring for signs of rats proceeded for a further two years and the island was declared rat-free in November 2018. The project encompassed partnerships between government agencies, industry and non-government organisations, and involved a significant volunteer contribution.

“1st century BCE occurrence of chicken, house mouse and black rat in Morocco: Socio-economic changes around the reign of Juba II on the site of Rirha”

This paper provides new data on the human-mediated introduction of chicken (Gallus gallus domesticus Linnaeus, 1758), black rat (Rattus rattus Linnaeus, 1758) and house mouse (M. musculus domesticus Schwarz & Schwarz, 1943) on the stratified site of Rirha, located in the Gharb plain, Morocco. The Mauretanian Tell, with its mud brick houses, streets, kitchens and dump areas have been excavated extensively and benefitted of sieving which provided clear evidence of the presence of the galliform and of the two murids in 1st century BCE levels and probably earlier around the 3rd 2nd c BCE for house mouse. This renews our understanding of the phylogeography of these three allochthonous species in Morocco. At a larger scale, our results feed the archaeological understanding of the occupation of this diachronic site and the evolution of the dynamics of trade and exchange prior to the Roman period in this area of northern Africa.

Native and Invasive Small Mammals in Urban Habitats along the Commercial Axis Connecting Benin and Niger, West Africa

Based on compiled small mammal trapping data collected over 12 years from Benin and Niger (3701 individual records from 66 sampling sites), located in mainland Africa, we here describe the small mammal community assemblage in urban habitats along the commercial axis connecting the two countries, from the seaport of Cotonou to the Sahelian hinterland, with a particular focus on invasive species. In doing so, we document extant species distributions, which highlight the risks of continuing the range expansion of three synanthropic invasive rodent species, namely black rats (Rattus rattus), brown rats (R. norvegicus), and house mice (Mus musculus). Using various diversity estimates and community ecology approaches, we detect a latitudinal gradient of species richness that significantly decreased Northward. We show that shrews (Crocidura) represent a very important component of micro-mammal fauna in West African towns and villages, especially at lower latitudes. We also demonstrate that invasive and native synanthropic rodents do not distribute randomly in West Africa, which suggests that invasive species dynamics and history differ markedly, and that they involve gradual, as well as human-mediated, long distance dispersal. Patterns of segregation are also observed between native Mastomys natalensis and invasive rats R. rattus and R. norvegicus, suggesting potential native-to-invasive species turn over. Consequences of such processes, especially in terms of public health, are discussed.

The Roman introduction and exportation of animals into Tunisia: Linking archaeozoology with textual and iconographic evidence

The Mediterranean basin was the core of the Roman Empire. Large communication networks were constructed and maintained that enabled the trade and distribution of large number of products between distant territories. North Africa, and more specifically Tunisia, was an important trading area. However, little information is available about the animal trade. To characterize this activity and evaluate its economic importance, in this study we examine which species were introduced and exported during the Roman era in Tunisia using archaeozoological data and contextualizing them with written and iconographic sources. This combined approach shows that the Romans were responsible for introducing and exporting numerous animals. We have documented the introduction of commensal animals, such as black rat (Rattus rattus) and house mouse (Mus sp.), wild animals such as fallow deer (Dama dama) and hare (Lepus sp.), and domestic animals such as rabbit (Oryctolagus cuniculus) and cat (Felis catus). At the same time, North Africa supplied Rome with wild beasts such as lions, tigers, bears and camels. We suggest that the animal trade was an important economic activity for Tunisia not only for the export of wild animals but also for the import of animals that were mainly used for social purposes.

Drivers of nest survival rate in a southern Tunisian population of Laughing Doves (Spilopelia senegalensis)

BackgroundInvestigating the ecological factors and processes shaping nest survival is of great importance for assessing the breeding success of bird populations and understanding their spatio-temporal dynamics. Here, this question is addressed for the Laughing Dove (Spilopelia senegalensis), an expanding Afro-tropical bird in the Tunisian oasis habitat.MethodsThis study took place in Kettana oasis, in south-eastern Tunisia. Natural Laughing Dove nests were searched for and monitored by means of regular visits, from the discovery date until the end of the breeding attempt (i.e. fledging or failure). Data were then used to investigate the relevance of laying date, nest age (days after clutch initiation), nest height and vegetation structure in the close nest tree environment as predictors of daily nest survival rate, using logistic-exposure models that accounted for heterogeneity in monitoring period among the studied nests. Models including different combinations of covariates were ranked according to their AICc scores, and the model-averaging technique was used for the assessment of the effects of covariates on daily nest survival rate.ResultsVegetation structure in the close nest tree environment and nest age provided important predictors of daily nest survival rate, whereas neither nest height nor laying date showed significant effects. Daily nest survival rate was negatively associated with the presence of date palm trees in the close nest tree environment, but it was positively related to nest age. Daily nest survival rate was higher during the post-hatching stage than during the pre-hatching stage.ConclusionsNests placed on fruit trees close to clumps of palm trees suffered higher predation risks compared to those placed on fruit trees situated far from palm trees. This is probably because palm tree clumps provided refuges for nest predators, notably the Black Rat (Rattus rattus) which has been reported to be the main nest predator in the oasis habitat. The predatory activity of this rodent seemed more directed against eggs than nestlings, which may explain the observed increase in daily survival rate with nest age.