Rattus Rattus Research Articles

Predation attempts on Hoopoe <i>Upupa epops</i> nests in a rural Mediterranean area of central Italy

Seventeen predation attempts on four Hoopoe Upupa epops nests in an heterogenous agricultural Mediterranean area of central Italy were recorded during breeding seasons 2020-21. Camera traps identified 7 different predators’ species, mainly Western whip snake Hierophis viridiflavus and Black rat Rattus rattus. Uropygial secretions and hissing calls from chicks and incubating female inside the breeding cavity always saved the clutches, while no active defense was performed by parents if outside the nest.

Morphologic and Genetic Characterization of Protospirura canariensis n. sp. (Nematoda, Spiruridae), a Parasite of the Black Rat Rattus rattus (Rodentia, Muridae) from El Hierro Island (Canary Archipelago, Spain)

A new spirurid nematode, Protospirura canariensis n. sp., a parasite of the black rat Rattus rattus Linnaeus, 1758 (Rodentia: Muridae), in El Hierro Island (Canary Archipelago, Spain), was described by means of light (LM) and scanning electron microscopy (SEM). The most discriminating characteristics between the new species and the remaining species of the genus Protospirura were observed to be the following: (a) the number of tooth-like outgrowths in the sub-median and lateral lobes of the pseudolabia, both in males and females (2 and 4, respectively); (b) the size of the right and left spicules in males (643–715 µm and 309–412 µm, respectively); and (c) the numbers and arrangements of the cloacal papillae in males. The new species has a total of 17 cloacal papillae (4 large and pedunculated pairs of precloacal papillae, an unpaired precloacal papilla and 4 pairs of postcloacal papillae). The arrangement of the postcloacal papillae are as follows: the first pair are large, pedunculated and placed near the posterior edge of cloaca; the three remaining postcloacal pairs are grouped and located near the posterior tip. In the latter group, the papillae in the first pair are large and pedunculated. The parasitized hosts and their geographical distributions were also useful criteria in distinguishing P. canariensis n. sp. from the remaining species of the genus Protospirura. In addition, the cytochrome c oxidase subunit I (cox1) sequence of the new species was obtained and compared with the available data of related species.

Vkorc1 gene polymorphisms confer resistance to anticoagulant rodenticide in Turkish rats.

Mutations in Exon 1, 2 and 3 of the vitamin K epoxide reductase complex subunit 1 (Vkorc1) gene are known to lead to anticoagulant rodenticide resistance. In order to investigate their putative resistance in rodenticides, we studied the genetic profile of the Vkorc1 gene in Turkish black rats (Rattus rattus) and brown rats (Rattus norvegicus). In this context, previously recorded Ala21Thr mutation (R. rattus) in Exon 1 region, Ile90Leu mutation (R. rattus, R. norvegicus) in Exon 2 region and Leu120Gln mutation (R. norvegicus) in Exon 3 region were identified as "missense mutations" causing amino acid changes. Ala21Thr mutation was first detected in one specimen of Turkish black rat despite the uncertainty of its relevance to resistance. Ile90Leu mutation accepted as neutral variant was detected in most of black rat specimens. Leu120Gln mutation related to anticoagulant rodenticide resistance was found in only one brown rat specimen. Furthermore, Ser74Asn, Gln77Pro (black rat) and Ser79Pro (brown rat) mutations that cause amino acid changes in the Exon 2 region but unclear whether they cause resistance were identified. In addition, "silent mutations" which do not cause amino acid changes were also defined; these mutations were Arg12Arg mutation in Exon 1 region, His68His, Ser81Ser, Ile82Ile and Leu94Leu mutations in Exon 2 region and Ile107Ile, Thr137Thr, Ala143Ala and Gln152Gln mutations in Exon 3 region. These silent mutations were found in both species except for Ser81Ser which was determined in only brown rats.

Examination of Horizontal Transmission of Nippostrongylus brasiliensis in Mice to Assess Biosecurity Risks.

Mice are commonly infected with Nippostrongylus brasiliensis (Nb) to study their immune responses. However, biosecurity measures have not been established for housing Nb-infected mice and rats. Transmission reportedly does not occur when infected mice are cohoused with naive mice. To test this, we inoculated female NOD. Cg-Prkdcscid Il2rgtm1Wjl /Sz(NSG;n = 12) and C57BL/6J (B6;n = 12) mice with 750 Nb L₃ larvae. These mice were then cohoused with naïve NSG ( n = 24) and B6 ( n = 24) mice (1 infected and 2 naïve mice per cage (24 cages) for 28 d in static microisolation cages that were changed every 14 d. We also did several studies to determine the conditions that favor horizontal transmission. First, we assessed in vitro development to the L₃ stage of Nb egg-containing fecal pellets maintained under 4 environmental conditions (dry, moist, soiled bedding, and control). Second, we assessed infection of naïve NSG mice ( n = 9) housed in microisolation cages that contained soiled bedding spiked with infective L₃ larvae (10,000/cage). Third, we gavaged NSG mice ( n = 3) with Nb eggs to model the potential for infection after coprophagy. We found that naïve NSG (9 of 24) and B6 (10 of 24) mice cohoused with an infected cagemate passed Nb eggs in feces as early as 1 d after cohousing and intermittently thereafter for varying periods. This shedding was presumably the result of coprophagy because adult worms were not detected in the shedding mice at euthanasia. Although eggs developed in vitro into L₃ larvae under moist and control environmental conditions, none of the NSG mice housed in cages with L₃ -spiked bedding or gavaged with eggs became infected with Nb. These findings indicate that infectious horizontal transmission does not occur when mice are housed with Nb-shedding cage mates in static microisolation cages with a 14-d cage-changing interval. Results from this study can be used to inform biosecurity practices when working with Nb-infected mice.

Biological invasions in international seaports: a case study of exotic rodents in Cotonou

Black rat (Rattus rattus), brown rat (Rattus norvegicus), and house mouse (Mus musculus) are known to be among the most common anthropophilic rodent species in cities worldwide. These species are responsible for the destruction of domestic and industrial materials, considerable damage to food stocks as well as zoonotic pathogens circulation and transmission to humans and animals. These invasive species have disseminated in all continents following human-mediated exchanges, especially maritime transports. In particular, seaports appear as privileged rats and mice’s entry points into new regions, thus making them international regulations’ priorities for rodent surveillance and management. Yet, studies on seaport rodents are rare; in particular, investigations on their genetic structure are almost inexistent, thus precluding science-guided interventions. In order to fill such a gap, our study focused on the population genetics of R. rattus, R. norvegicus and M. musculus in the Autonomous Port of Cotonou, Benin. Nine different sites were surveyed for three years. In total, 366 R. rattus, 188 R. norvegicus and 244 M. musculus were genotyped using 18 microsatellites, 16 microsatellites and 17 microsatellites, respectively. Our results show very well-structured genetic clusters in all three species as well as limited impacts of rodent control campaigns. Using comparisons with genotypes from other European, Asian and African countries, we suggest for the first time that settlement of newly introduced individuals may be a rare event. Implications in terms of management units and control and monitoring are discussed.

Impairment of the Reproductive System and Mating of Male and Female Black Rats Treated with Lambda-Cyhalothrin Bait and Its Field Application

Impairment of the Reproductive System and Mating of Male and Female Black Rats Treated with Lambda-Cyhalothrin Bait and Its Field Application

Rodent management in Aotearoa New Zealand: approaches and challenges to landscape-scale control.

Aotearoa-New Zealand has only four rodent species, all introduced. In order of arrival, they are Pacific rat Rattus exulans, brown rat R. norvegicus, house mouse Mus musculus, and black rat R. rattus. Rodent management in New Zealand aims mainly to conserve indigenous biodiversity rather than to protect crops or manage diseases, as is usual elsewhere. We describe four major "regimes" and one major vision for rodent control in New Zealand to meet ecological restoration objectives. Current challenges for island eradications are for large islands that are remote or populated by people. Aerial 1080 is the only large-scale (tens of thousands of hectares) option for black rat control, but its application requires adjustment to counter subsequent rapid black rat repopulation. Unfenced "ecosanctuaries" (mean 720 ha) use ground-based traps and poisons to target mainly black rats and face constant reinvasion. Ecosanctuaries with mammal-resistant fences (up to 3500 ha) limit reinvasion and target more pest species and have enabled the return of previously extirpated taxa to the main islands. Predator Free 2050 aims to eradicate the rat species (but not mice) plus some other introduced mammals from New Zealand by 2050. This vision is not attainable with current tools, but research and experimental management is exploring techniques and technologies. The large scale (to 100000 ha) at which black rats are now targeted for control to extremely low abundance seems to be unique to New Zealand.

Concentrations and isomer profiles of perfluoroalkyl carboxylates in house rats (Rattus norvegicus) and human blood: Implication for human exposure sources

In humans, perfluoroalkyl acids (PFAAs) are derived from direct external exposure and subsequent degradation of their precursors, but the contribution of the sources remains unclear. Here, we examined PFAA concentrations and isomer profiles in house rat (Rattus norvegicus; n = 29, a similar source of human exposure to PFAAs) and human blood (n = 194), and explored the sources of PFAAs in humans. Perfluorooctane sulfonate (PFOS, 19–49 %) was the predominant PFAA in rat tissues, with the highest concentrations of ΣPFAAs in the liver (sum of PFAAs, mean 20–212 ng/g wet weight (ww)). Perfluorooctanoate (PFOA, mean 2.6 ng/mL) was the major PFAA in human blood. Differences in composition profiles of PFAAs indicate that distribution behaviors of the compounds is different among different tissues. In addition, the average percentage of branched PFOA and PFOS in rat tissues was 3.1–6.7 % and 20–37 %, respectively, compared to 4.1 % and 25 % in human blood. Our study suggests that perfluoroalkyl carboxylates in house rats and humans may be primarily due to atmospheric degradation of fluorotelomer alcohol-based chemicals.

Radio collaring reveals long-distance movements of reinvading ship rats following landscape-scale control

Radio collaring reveals long-distance movements of reinvading ship rats following landscape-scale control

Stowaways: Maritime ecology of the oldest commensal ship rats (Rattus rattus) found on a Mediterranean shipwreck

Ship rats (Rattus rattus) have successfully colonized six continents and 80% of islands worldwide by stowing-away on anthropogenic vessels. Numerous zooarchaeological and metagenomic studies have contributed to tracing the western dispersal of ship rats out of the Indian subcontinent and into the Mediterranean Basin, North Africa, and Europe. This has increased understanding of historical maritime mobility, trade contacts, and the spread of pandemic disease such as the plague. Moreover, considerable research has been conducted on the behavior, ecology, and population dynamics of ship rats in invaded areas, which supports conservation and eradication efforts. However, few studies have shed light on the mode of travel in between the geographic origins and destinations of ship rats, such as ships and boats, which act as mobile, commensal habitat for this cosmopolitan species. We address this lacuna here, by analyzing an assemblage of ship rat remains from an early Islamic period shipwreck, the Ma‘agan Mikhael B, located on the Carmel coast of modern Israel. Using zooarchaeological, biometrical, and palaeogenetic (aDNA) methodologies, we investigated the maritime ecology of ship rats regarding dispersal behavior, habitat selection, source–sink dynamics, and relative body size. The results of this study suggest that ship rats actively inhabited the Ma‘agan Mikhael B as part of their habitat selection processes, that conditions onboard provided high-quality habitat (adequate food and harborage, likely absence of predators and disease), and that they appear to have exhibited a degree of gigantism, possibly due to ‘island rule’. This study has implications for future metapopulation genetic studies on ship rats, as well as shows the value of zooarchaeological analysis in understanding the ecological circumstances of the maritime mobility of ship rats in the Mediterranean region.

Hepatorenal and Testicular Dysfunctions of Clodinafop-Propargyl Bait in Male Black Rat, Rattus rattus and Its Field Efficiency

) has become in a commensal relationship with humans and has been responsible for obvious damage to agriculture annually. In this study, clodinafop-propargyl bait (0.98%) was introduced to the adult male rats for seven days under laboratory conditions using a non-choice feeding method. The impact of the compound on the body and some organs' weights and functions was studied. Histopathological changes of the liver, kidney, and testis as well as sperm count, sperm morphology, vitality and motility percent were recorded. The efficiency of clodinafop-propargyl bait (0.98%) was evaluated under field conditions of crop stores. The results demonstrated that the body weight and testis of rats significantly decreased obviously after treatment. As well as, the treatment caused immoderate loss of water through the skin, losing appetite and slow movement of rats. While weights of the liver and kidney of treated rats significantly increased. In addition, the appearance of morphological and histopathological alterations in the liver, kidneys, and testis were observed. Also, significant elevation in serum (ALT and AST) enzymes, urea, creatinine and uric acid levels compared with control after treatment were recorded. Furthermore, sperm count, motility and vitality percentages significantly decreased (p≤0.05) in treated rats compared with controls. There were perspicuous abnormalities in the form of the head, neck, and tail of the spermatozoa in the treated rats. Regarding, sperm motility; non-progressive and immotile grades were significantly increased in treated rats compared with controls. Moreover, clodinafop-propargyl bait (0.98%) proved efficient under crop store conditions as it caused an 86.78 % reduction in the rat population. In conclusion, clodinafop-propargyl bait has a strong toxic impact on the liver, kidneys and reproductive system of male black rats affecting their fertility by destroying testicular integrity and function. Furthermore, the field results proved these impacts and achieved good results. We can conclude that this compound can be used in the control of black rats and can be used in rodent control programs.

English

The aim of this study is to phenotypically characterize Klebsiella isolates from rats. A survey  was  conducted on 100 swaps samples  obtained  from  captured  house  rats  in University of Abuja main campus from May to August 2021. Isolation and identification of the Klebsiella species was done using conventional cultural and biochemical techniques. Of the 100 samples analyzed, 20 (20%) were positive for Klebsiella, 12% of the isolates were identified as Klebsiella Pneumonia while 8% were identified as Klebsiella oxytoca. Isolates were further confirmed by Microbact 24E test kit identification system (Oxiod, UK). Klebsiella isolates encountered in this study were further subjected to antimicrobial susceptibility testing using modified single disk diffusion method. Result of the antimicrobial susceptibility testing showed that the Klebsiella species were resistant to chloramphenicol (80%), gentamycin (90%), augmentin (80%), Cotrimoxazole (70%) and amoxicillin (70%). However, the Isolates were susceptible to Pefloxacin (100%), Streptomycin (40%), Ofloxacin (100%), Ciprofloxacin (100%) and Sparfloxacin (80%). Conclusively, this study documented the occurrence and existence of multiple resistant strains of K. Pneumonia and K. Oxytoca in rats in our environment and it is therefore of public health concern.   Key words: Klebsiella species, household rat, Rattus rattus, antimicrobial susceptibility.

Prevalence of Ectoparasites on Small Mammals Inhabiting an Agroforestry System of Western Portugal

The goal of this study was to assess ectoparasite-small mammal host associations in central-west Portugal in native and exotic habitats, respectively, including a cork oak woodland and a Eucalyptus plantation. Mammals were sampled with Sherman and pitfall traps, and ectoparasites were collected and identified in all samples. We trapped 681 small mammals: 5 rodent species - wood mouse, Apodemus sylvaticus (N = 527); the Algerian mouse, Mus spretus (N = 67); Cabrera's vole, Microtus cabrerae (N = 8); the Lusitanian pine vole, Microtus lusitanicus (N = 2); and the black rat, Rattus rattus (N = 1) - and 1 insectivore species - the greater white-toothed shrew, Crocidura russula (N = 76). We identified 4 flea species (Nosopsyllus fasciatus, Ctenophthalmus sp., Typhloceras favosus, and Typhloceras poppei); 5 tick species (Haemaphysalis punctata, Ixodes ricinus, Ornithodoros sp., Rhipicephalus pusillus, and Rhipicephalus sanguineus); and 1 chigger species (Neotrombicula sp.) from hosts. The wood mouse was the small mammal species with the highest overall ectoparasite prevalence, although ticks were the least prevalent taxon. We found that ectoparasite guilds represented a somewhat generalist host pattern, and chiggers presented some host specificity. The data presented herein increase the knowledge regarding ectoparasite prevalence and distribution among small mammal hosts in the Mediterranean. Although surveys of ectoparasites of small mammals in central-west Portugal are not novel, this is the first time that a species belonging to the genus Ctenophthalmus is reported from M. cabrerae (Cabrera's vole) in Portugal.

Genotypic detection of barriers to rat dispersal: Rattus rattus behind a peninsula predator-proof fence

Clear delimitation of management units is essential for effective management of invasive species. Analysis of population genetic structure of target species can improve identification and interpretation of natural and artificial barriers to dispersal. In Aotearoa New Zealand where the introduced ship rat (Rattus rattus) is a major threat to native biodiversity, effective suppression of pest numbers requires removal and limitation of reinvasion from outside the managed population. We contrasted population genetic structure in rat populations over a wide scale without known barriers, with structure over a fine scale with potential barriers to dispersal. MtDNA D-loop sequences and microsatellite genotypes resolved little genetic structure in southern North Island population samples of ship rat 100 km apart. In contrast, samples from major islands differed significantly for both mtDNA and nuclear markers. We also compared ship rats collected within a small peninsula reserve bounded by sea, suburbs and, more recently, a predator fence with rats in the surrounding forest. Here, mtDNA did not differ but genotypes from 14 nuclear loci were sufficient to distinguish the fenced population. This suggests that natural (sea) and artificial barriers (town, fence) are effectively limiting gene flow among ship rat populations over the short distance (~ 500 m) between the peninsula reserve and surrounding forest. The effectiveness of the fence alone is not clear given it is a recent feature and no historical samples exist; resampling population genetic diversity over time will improve understanding. Nonetheless, the current genetic isolation of the fenced rat population suggests that rat eradication is a sensible management option given that reinvasion appears to be limited and could probably be managed with a biosecurity programme.

Improved status of the conservation reliant Oahu Elepaio through effective management and natural adaptation

AbstractThe Oahu Elepaio (Chasiempis ibidis) is an endangered forest bird endemic to the Hawaiian island of Oahu. The two most serious threats to the Oahu Elepaio are nest predation by nonnative black rats (Rattus rattus) and avian pox (Avipoxvirus spp.), a disease carried by nonnative mosquitoes. The Oahu Elepaio is conservation reliant because its continued existence depends on rat control. We used 27 years of data from 1995 to 2021 on pox prevalence, nest success, and fecundity with versus without rat control to reexamine the severity of these threats. Prevalence of avian pox declined over time. From 1995 to 2004, pox prevalence averaged 21% ± 4% per year and was positively related to annual rainfall. From 2005 to 2021, pox prevalence was only 2% ± 0.1% and despite several wet years there was no relationship with rainfall. The Oahu Elepaio appears to have evolved resistance to the pox variant currently in Hawaii. Elepaio nest success was higher with rat control (58% ± 1%) than without rat control (42% ± 6%). Nest success did not differ significantly between native tree species (52% ± 6%) and nonnative tree species (58% ± 6%) or between fruiting tree species (58% ± 1%) and nonfruiting species (61% ± 6%). Elepaio annual fecundity was higher with rat control (0.78 ± 0.02) than without rat control (0.48 ± 0.04) and varied among sites and years. The two primary threats to the species have been ameliorated through a combination of effective management and natural adaptation. The species' status should continue to improve if management is maintained, and someday, if patterns of natural adaptation continue, it could break free from conservation reliance.

Immigration drives ship rat population irruptions in marginal high‐elevation habitat in response to pulsed resources

AbstractPest animal populations, such as rodents, often irrupt in response to pulsed resources. However, few studies have considered how understanding the propagation of irruptions across landscapes could lead to more efficient pest suppression. Resource pulses might create temporary source–sink dynamics in heterogeneous environments, whereby reservoirs of animals living in high‐quality habitat increase and spill over into more marginal habitat. Low‐density populations in marginal habitat could also increase through in situ breeding by residents in response to increased food availability. Understanding the relative importance of these two nonmutually exclusive processes is important as pest outbreaks could potentially be more efficiently controlled by targeting source populations early in an outbreak. We used a Bayesian hierarchical model to estimate the importance of density‐dependent emigration from lower elevation habitats versus in situ breeding by resident animals to the population growth of invasive ship rats (Rattus rattus) in marginal, high elevation habitats during a pulsed resource event (beech seed mast). We found that emigration from lower elevations was important for facilitating rapid population growth at high elevations, enabling rats to reach peak densities of 10.6 rats ha−1. Without immigration, rats were predicted to reach peak densities of only 1.8 rats ha−1 at high elevation, given their densities in that habitat when we started monitoring (0.6 rats ha−1). This result suggests that rat control that targets low and mid‐elevations only may be sufficient to suppress irruptions in high‐elevation habitat if control effectively prevents immigration. Our study suggests spillover from higher quality habitats may enable outbreaks to rapidly propagate over landscapes. However, for r‐selected taxa such as rodents, even very low densities of animals living in marginal habitats can increase significantly when resource pulses occur, albeit at lower densities than for populations in higher quality habitat.

An invasive human commensal and a native marsupial maintain tick populations at the urban fringe.

Ticks (Acari: Ixodidae) are major disease vectors globally making it increasingly important to understand how altered vertebrate communities in urban areas shape tick population dynamics. In urban landscapes of Australia, little is known about which native and introduced small mammals maintain tick populations preventing host-targeted tick management and leading to human-wildlife conflict. Here, we determined (1) larval, nymphal, and adult tick burdens on host species and potential drivers, (2) the number of ticks supported by the different host populations, and (3) the proportion of medically significant tick species feeding on the different host species in Northern Sydney. We counted 3551 ticks on 241 mammals at 15 sites and found that long-nosed bandicoots (Perameles nasuta) hosted more ticks of all life stages than other small mammals but introduced black rats (Rattus rattus) were more abundant at most sites (33%-100%) and therefore important in supporting larval and nymphal ticks in our study areas. Black rats and bandicoots hosted a greater proportion of medically significant tick species including Ixodes holocyclus than other hosts. Our results show that an introduced human commensal contributes to maintaining urban tick populations and suggests ticks could be managed by controlling rat populations on urban fringes.

Infestation of Oriental House Rat (Rattus tanezumi) with Chigger Mites Varies along Environmental Gradients across Five Provincial Regions of Southwest China.

Chigger mites are the exclusive vector of scrub typhus. Based on field investigations of 91 survey sites in 5 provincial regions of Southwest China, this paper reported variations of chigger infestation on the oriental house rat (Rattus tanezumi) along various environmental gradients. A total of 149 chigger species were identified from 2919 R. tanezumi in the 5 provincial regions, and Leptotrombidium deliense (a major vector of scrub typhus in China) was the first dominant chigger species, followed by Ascoschoengastia indica and Walchia ewingi. Rattus tanezumi had a stable overall prevalence (PM = 21.10%), mean abundance (MA = 7.01), and mean intensity (MI = 33.20) of chiggers with the same dominant mites in the whole Southwest China in comparison with a previous report in Yunnan Province, but chigger infestations on R. tanezumi varied along different environmental gradients. Rattus tanezumi in mountainous landscape had a higher infestation load of chiggers with higher species diversity than in flatland landscape. The infestation was higher at lower altitudes and latitudes. A high intensity of vegetation coverage was associated with high infestations. The results reflect the environmental heterogeneity of chiggers on the same host species. Warm climate and high relative humidity are beneficial to chigger infestation on R. tanezumi.

Activity and movement of small mammal tick hosts at the urban fringes of Sydney, Australia

Context Small mammals may traverse the urban fringe and use both natural and anthropogenic resources. In Australia, human commensal black rats (Rattus rattus) and native long-nosed bandicoots (Perameles nasuta) are important tick hosts, which can be found persisting at the urban fringe, leading to human–wildlife conflict. Aims We aimed to (1) determine the relative activity of small mammals in yards and associations with yard attributes, (2) compare activity of black rats and long-nosed bandicoots in bushland with activity in yards and (3) determine the proportion of black rats and long-nosed bandicoots that crossed the urban fringe. We predicted that native bandicoots would be more active in bushland habitats and that black rats would be more active in yards. Methods We used camera trapping in 56 residential yards, 18 of which were paired with adjacent bushland to measure small mammal activity in the two habitats. We recorded yard attributes and examined these associations using generalised linear models. We used isodar analysis to investigate black rat preferences of bushland habitat compared with yards, and we used Rhodamine B baiting to investigate movement at the urban fringe. Key results We found that black rats were the most active small mammal in residential yards and were detected in more yards than other small mammals, followed by bandicoots. Black rat activity was greater in yards adjacent to bushland, but no other yard attributes were associated with black rat and bandicoot activity. Overall, activity tended to be higher in bushland than in yards at paired locations. Conclusions Our findings suggest residential yards likely provide high-quality resources for long-nosed bandicoots. Low rates of movement at the urban fringe (6%), and a preference for bushland at low densities suggests that black rats may be synanthropic rather than commensal, occupying an urban niche but not depending on anthropogenic resources as expected. Implications Residential properties located adjacent to bushland may be exposed to increased black rat activity in yards. Future work should consider how introduced rats may be controlled in bushland to assist urban rat control efforts and avoid non-target impacts. Residential yards are likely to be important habitat for the persistence of long-nosed bandicoots in urban environments.

Investigating the impact of black rats (Rattus rattus) on the endemic and threatened avifauna of Christmas Island

Context Invasive mammalian predators are a primary cause of extinctions, especially on islands. Baseline data on the impact of invasive mammalian predators are critical for deciding whether their eradication or control should be attempted, and for monitoring ecosystem changes over time if control does occur. Christmas Island is a tropical island with multiple invasive species, including two mammalian predators (black rats, Rattus rattus and feral cats, Felis catus). Black rats are known to prey upon island bird species (including their nests) elsewhere, but the severity of their impacts on Christmas Island birds is unclear. Describing these impacts would help managers decide whether rat control is warranted, especially as a cat eradication program underway on the island could conceivably result in increased rat density. Aims In this study, we quantify the impacts of rats on Christmas Island bird abundance and nesting success. Methods The abundance of four endemic forest bird species/subspecies (Christmas Island imperial pigeon, Ducula whartoni, emerald dove, Chalcophaps indica natalis, thrush, Turdus poliocephalus erythropleurus and white-eye, Zosterops natalis) was measured using transect surveys. Nest success was measured using remote sensing camera surveillance for one forest bird species (thrush) and one seabird species (red-tailed tropicbird, Phaethon rubicaudra westralis). We explored whether these measures were related to spatial variation in rat density and activity (measured by trapping and inkcards), the presence of other invasive species, habitat and seasonal variables. Key results Neither rat density nor activity explained the abundance of any forest bird species. Instead, seasonal and habitat features were more consistent predictors of bird abundance. White-eyes were more abundant near yellow crazy ant (Anoplolepis gracilipes) supercolonies. Nest success for thrushes and red-tailed tropicbirds was either not, or only very weakly, influenced by rats. Conclusions Black rats currently have little effect on the population sizes and nesting success of Christmas Island birds. Implications This study suggests that rat control is not currently a management priority, but ongoing monitoring of rat density, activity, and impacts is needed to ensure management can respond promptly if rat density or impacts change as cat control progresses towards eradication.