Introduced House Mice Mus Musculus Research Articles

Natural recolonisation of sub-Antarctic Marion Island by Common Diving Petrels Pelecanoides urinatrix

Nocturnal burrow-nesting seabirds are notoriously difficult to study and can go unnoticed for years in remote areas. One of these species is the Common Diving Petrel Pelecanoides urinatrix, which has a circumpolar breeding distribution in the Southern Ocean, including at the sub-Antarctic Prince Edward Islands. At Marion Island, the larger of the two islands, the species was extirpated by cats that were introduced in 1948. The cats were eradicated by 1991, and Common Diving Petrels were discovered in burrows in coastal Poa cookii (Cook’s tussock grass) on a steep south-facing slope in Goodhope Bay during April 2015. Subsequent surveys in October 2015 and February 2016 confirmed breeding over a 1-ha area. In 2019/2020, breeding phenology and success was studied in 36 nests at the same site. Birds called from their burrows from mid-September, laying started in early October, and the first chick was observed on 20 December. Hatching peaked in early January and chicks fledged from the end of February to mid-March. This breeding phenology is similar to that at the neighbouring Crozet Archipelago. Overall nest survival was 46.4 ± 9.2% (mean ± SE; 95% CI: 29.5–64.1%), with most failures happening around hatching time. Further monitoring is needed to assess whether introduced House Mice Mus musculus contributed to the low hatching success. Common Diving Petrels were discovered breeding in other coastal areas, mostly in the south and east of the island. It is unlikely that breeding by this species was overlooked for three decades, suggesting that the elimination of cats allowed Common Diving Petrels to recolonise the island.

Evaluating population impacts of predation by owls on storm petrels in relation to proposed island mouse eradication

AbstractWe quantify the expected demographic benefit to a seabird of conservation concern, the ashy storm‐petrel Oceanodroma homochroa, from the proposed eradication of introduced house mice Mus musculus on the South Farallon Islands, California. A key objective of the eradication is to reduce storm petrel predation by burrowing owls Athene cunicularia, which stopover on the island during their fall migration. Mouse trapping and field surveys of both owls and depredated storm petrel carcasses conducted during 2000–2012 reveal a strongly seasonal, inter‐related pattern among the three species: When owls arrive during the fall, mice are super‐abundant and the overwhelming choice of prey for those owls that remain. In the winter, the mouse population crashes just as storm petrels begin to arrive in large numbers; owls that remain on the island switch to preying upon storm petrels until May, when they depart to breed. Capture–recapture analyses of storm petrels showed (1) annual adult survival was inversely related to owl abundance, especially during January–April, and (2) storm petrels demonstrated a declining trend in abundance 2006–2012. The latter was associated with low rates of adult survival, high abundance of overwintering burrowing owls, and high incidence of depredated storm petrels. To evaluate projected impacts to storm petrels of a change in owl predation, we developed a Leslie matrix model, incorporating environmental stochasticity. We modeled future storm petrel population trajectories, allowing for different levels of owl‐mediated predation. Our results suggest that a reduction in owl abundance, a projected consequence of the elimination of mice, has the potential to substantially reduce overall storm petrel mortality, thereby reducing storm petrel declines and increasing the likelihood of stable trends in the future. While long‐term benefits to storm petrels of mouse eradication are apparent, the risk of increased predation due to prey‐switching by owls also needs to be addressed. This study highlights uncertainty of outcomes, which must be considered in evaluating management impacts. This study demonstrates the value of concurrent, continuous, long‐term datasets in providing a quantitative basis for management to aid the conservation of species of concern.

Drivers of predatory behavior and extreme size in house mice Mus musculus on Gough Island

Abstract In comparison to the mainland, populations of rodents on islands are often characterized by a suite of life history characteristics termed the “island syndrome.” Populations of rodents introduced to islands are also well known for their impacts on native species that have evolved in the absence of mammalian predators. We studied the ecology and behavior of introduced house mice Mus musculus on Gough Island where they are the only terrestrial mammal and where their predatory behavior is having a devastating impact on the island’s burrowing petrel (order Procellariiformes ) population and the Critically Endangered Tristan albatross Diomedea dabbenena . Mice on Gough exhibit extreme features of the island syndrome, including: a body mass 50–60% greater than any other island mouse population, peak densities among the highest recorded for island populations, and low seasonal variation in numbers compared to other studied islands. Seasonal patterns of breeding and survival were linked to body condition and mass, and mice in areas with high chick predation rates were able to maintain higher mass and condition during the winter when mouse mortality rates peak. Within-site patterns of chick predation indicate that proximity to neighboring predated nests and nesting densities are important factors in determining the likelihood of predation. We conclude that selection for extreme body mass and predatory behavior of mice result from enhanced overwinter survival. Small mammal populations at temperate and high latitudes are normally limited by high mortality during the winter, but on Gough Island mice avoid that by exploiting the island’s abundant seabird chicks.

Low burrow occupancy and breeding success of burrowing petrels at Gough Island: a consequence of mouse predation

SummaryThe predatory behaviour of introduced house mice Mus musculus at Gough Island is known to impact on albatross and petrels, resulting in the Tristan Albatross Diomedea dabbenena and Atlantic Petrel Pterodroma incerta being listed as “Critically Endangered” and “Endangered”, respectively. Although predation has been documented for two burrowing petrels and one albatross species, the impact of house mice on other burrowing petrels on Gough Island is unknown. We report burrow occupancy and breeding success of Atlantic Petrels, Soft-plumaged Petrels Pterodroma mollis, Broad-billed Prions Pachyptila vittata, Grey Petrels Procellaria cinerea and Great Shearwaters Puffinus gravis. With the exception of the Great Shearwater, breeding parameters of burrowing petrels at Gough Island were very poor, with low burrow occupancy (range 4–42%) and low breeding success (0–44%) for four species, and high rates of chick mortality in Atlantic Petrel burrows. Breeding success decreased with mass, suggesting that smaller species are hardest hit, and winter-breeding species had lower breeding success than summer breeders. The results indicate that introduced house mice are having a detrimental impact on a wider range of species than previously recorded and are likely to be causing population declines among most burrowing petrels on Gough Island. The very low values of burrow occupancy recorded for Soft-plumaged Petrels and Broad-billed Prions and greatly reduced abundance of burrowing petrels in comparison to earlier decades indicate that Gough Island’s formerly abundant petrel populations are greatly threatened by the impact of predatory house mice which can only be halted by the eradication of this species from the island.

Predation of Atlantic Petrel chicks by house mice on Gough Island

The impacts of predation by invasive mammals on island fauna are a major driver of insular biodiversity loss. Devastating, hitherto unsuspected impacts of predatory house mice on breeding seabirds have been described recently. We studied the fate of 178 Atlantic Petrel Pterodroma incerta nests at Gough Island, over four seasons, from October 2003 to January 2008. Introduced house mice Mus musculus were found in all study burrows checked for mouse visits. From October 2003 to September 2004, we video-recorded attacks by mice on six (of 13) live, healthy Atlantic Petrel chicks and on one (of three) great shearwater Puffinus gravis chicks. In all years, chicks died from mouse attacks. Stage-specific daily nest survival rates were modelled, from which estimates of breeding success were derived that accounted for the variable exposure periods studied among years. Average daily survival rate of eggs was 0.998, and hatching success through the entire incubation period (55.5 days) was 0.924 [95% confidence interval (CI) 0.903–0.940]. Daily chick survival rates were 0.990, which gave a modelled fledging success of 0.247 (CI 0.165–0.338) over the 138-day chick period, and average annual breeding success (chicks fledged per breeding attempt) of 0.228 (CI 0.150–0.318), which is low compared with congeners. Productivity estimates were used as a parameter in a population simulation model, which predicted a population multiplication rate (λ) of 0.993 (CI = 0.966–1.021). However, in the one season studied from laying to fledging (2007), from 58 nests, only one chick fledged (1.7%). This suggests the wide errors on the model results may obscure a more severe reality. More than 60% of model simulations resulted in an International Union for Conservation of Nature classification of Endangered. Our results add support to calls to eradicate mice from Gough Island. More generally, mice cannot be ignored as a potential threat to island fauna, and island restoration and management plans should routinely include eradication of introduced mice.

A tale of two islands: contrasting fortunes for Subantarctic skuas at the Prince Edward Islands

Subantarctic skuas Catharacta antarctica are key predators of burrowing petrels at sub-Antarctic islands, and can be used to monitor the health of burrowing petrel populations. A survey of skuas at the Prince Edward Islands was conducted during December 2008, repeating a previous survey in December 2001. Prince Edward Island (46 km2) remains free of introduced mammals, whereas Marion Island (290 km2) had a feral population of cats from the 1950s to 1980s, and still supports a large population of introduced house mice Mus musculus. Breeding skuas were more widespread, occurred at greater densities and extended to higher elevations at Prince Edward Island than Marion Island. Prince Edward Island also supported twice as many non-breeding birds. Burrowing petrels comprised 96% of prey in skua middens at Prince Edward Island compared to only 22% on Marion Island where penguins are more important. The numbers of breeding pairs at Prince Edward Island increased from 2001 to 2008, probably as a result of better coverage in 2008, whereas the number of skua nests on Marion Island was barely half that counted in 2001, continuing an apparent decrease in this species at Marion Island since the 1980s. There is no evidence that removal of cats from Marion Island in the early 1990s has benefited the major native predator of burrowing petrels.

Evidence of mouse attacks on albatross chicks on sub-Antarctic Marion Island

Introduced house mice Mus musculus have recently been discovered to be significant predators of chicks of Tristan albatrosses Diomedea dabbenena and several burrowing petrels at Gough Island. We summarize evidence for mouse attacks on albatross chicks at sub-Antarctic Marion Island, where mice are also the only introduced mammal following the eradication of feral cats Felis catus in the early 1990s. Wounds consistent with mouse attacks have been found on wandering albatrosses Diomedea exulans since 2003 and dark-mantled sooty albatrosses Phoebetria fusca in 2009. To date, attacks on wandering albatross chicks have been infrequent, affecting <1% of chicks in study colonies, and only about half of the attacks have been fatal. Small chicks may also die when mouse burrows collapse under chicks, trapping them. Mouse attacks appear to be a recent phenomenon, supporting the contention that mice pose a significant threat when they are the only introduced mammal species. Ongoing monitoring is needed to assess whether the impacts of mice increase over time. Our observations add impetus to calls for the eradication of mice from Marion Island.

Small mammal populations in a eucalypt forest affected by fire and drought. I. Long-term patterns in an era of climate change

This paper reports a study of ground-dwelling, small mammals in coastal eucalypt forest in south-eastern Australia from 1970 through 2005. During this time, the study area burnt in an intense fire in December 1972 and was partially burnt in November 1980. Both fires were associated with prolonged drought. The mammals studied comprised two dasyurid marsupials, Antechinus agilis and A. swainsonii, two native murid rodents, Rattus fuscipes and R. lutreolus, and the introduced house mouse Mus musculus. After intensive sampling throughout the year from 1970 through 1972 to establish basic ecological and population parameters of the small mammal community, populations were sampled annually during late autumn and early winter before the onset of breeding. There were marked differences in the annual (autumn/winter) abundances of all species; numbers of A. agilis ranged from 4 to 142 individuals; A. swainsonii 0 to 43; R. fuscipes 4 to 54; R. lutreolus 0 to 11; M. musculus 0 to 23. Following the 1972 fire, numbers fell to the lowest level recorded during the study and each population subsequently disappeared from the plot between the 1973 and 1974 winter censuses. The less intense 1980 fire did not lead to extirpation, but numbers of A. agilis, A. swainsonii and R. fuscipes declined as drought conditions persisted through 1983. R. lutreolus occurred consistently only following the fires, when a grassy ground vegetation favoured by this species developed. Similarly, M. musculus colonised within two years of the fires and persisted on the plot for 3–4 years before disappearing. Following the fires, populations of the omnivorous R. fuscipes recovered first followed by the scansorial, insectivorous A. agilis and last by the fossorial, insectivorous A. swainsonii. Two primary conclusions emerged from this study. First, the intense fire of 1972 did not kill all the animals immediately, but led to the disappearance of each species from the plot over 18 months. Thus, intense fire had a delayed but catastrophic impact on small ground-dwelling mammals. The fluctuations in population levels, covering more than an order of magnitude, demonstrate that factors other than fire, such as rainfall and drought, drive the population dynamics of these small mammals. As stability and recovery are not features of local populations, long-term studies of benchmark populations are necessary to manage forest biodiversity.

Bait acceptance by house mice: an island field trial

Predation by introduced house mice Mus musculus on islands is one cause of decline in native birds and has deleterious impacts on other ecological aspects. Eradication of rats (Rattus spp.) from islands of up to >10000 ha has been achieved, but for mice scale is still an issue with the largest island cleared being only 710 ha. The feasibility of eradicating mice from larger islands is being considered, and to support these assessments, we undertook a field study on Gough Island (6400 ha) to determine whether all mice would be likely to accept toxic bait. We replicated a toxic bait operation as closely as possible, in timing, probable bait density and distribution, using a bait formulation used commonly in rodent eradication operations. Baits lacked toxin but were coated with the fluorescent dye rhodamine B. Mice trapped in and around the baited areas were inspected under ultraviolet light for fluorescent marking indicative of bait consumption. Of 434 mice, 97% tested positive, including mice trapped on assessment lines up to 90 m from the closest bait. There was no difference in the proportions of unstained mice from assessment lines outside baited sites compared with mice trapped in the core baited sites, suggesting large-scale foraging movements over relatively large distances into the baited sites from surrounding, non-baited habitat. Despite the high bait densities (15.7 kg ha−1 at initial application and 7.9 kg ha−1 at second application), bait consumption rates of ~4 kg ha−1 day−1 occurred after both applications. This was much higher than expected (probably the result of large-scale movements) and meant that all baits were consumed before trapping began. Thus the 13 unstained mice trapped in the core of the baited area may have moved there after bait was consumed. Further trials are required to assess whether all unmarked mice were false negatives (not exposed to bait) or if any were true negatives (rejected bait). A separate experiment found that all 11 mice trapped in a cave had eaten bait applied aboveground around the cave’s entrances, suggesting that caves do not serve as refugia for mice and are thus unlikely to compromise an eradication attempt.

Predatory Behaviour of the Gough MoorhenGallinula comeri: Conservation Implications

The Gough Moorhen is endemic to Gough Island and is classified by the IUCN as Threatened. We present several observations of Gough Moorhens preying on introduced House Mice Mus musculus and on eggs and chicks of burrow-nesting procellariiform seabirds. The incidence of egg predation is almost certainly related to incubation breaks or abandonment. We estimate that Moorhens could access and depredate unattended eggs of at least five species but levels of predation appear to be low and are unlikely to affect population parameters of impacted species. Moorhens hunting live mice and scavenging carcasses presents a significant conservation concern. A possible eradication of mice from Gough Island is likely to employ poisons that are toxic to the Moorhens. Therefore secondary poisoning of Moorhens, by eating poisoned mice, is a threat to the Gough Moorhens. An eradication effort will be required to take appropriate mitigation measures. The introduced Gough Moorhen population on Tristan da Cunha serves as an ex situ population and could, if required, be used to re-stock Gough.

INTERFERENCE COMPETITION BETWEEN INTRODUCED BLACK RATS AND ENDEMIC GALÁPAGOS RICE RATS

Replicated field experiments were used to quantify and to describe the mechanism of competition between the introduced black rat Rattus rattus and the endemic Santiago rice rat Nesoryzomys swarthi on Santiago Island, Galápagos Islands, Ecuador. The removal of R. rattus significantly slowed the rate of seasonal population decline in N. swarthi. This effect was particularly evident for female, relative to male, N. swarthi and appeared to be driven solely by enhanced immigration; no other fitness or space use parameters were affected. The candidate hypotheses to explain the mechanism of competition were exploitation competition, interference by resource defense, and interference by aggressive encounter. To distinguish between hypotheses, we conducted a replicated resource supplementation experiment with patchy food, scattered food, and no food (control) treatments. The opportunistic R. rattus responded to the extra resources with increased adult immigration and juvenile recruitment, resulting in a significant abundance boost of sevenfold on patchy grids and fourfold on scattered grids. Females increased in body mass, and the breeding season was lengthened. In contrast, there was no change in the abundance of N. swarthi and no obvious benefit to reproduction. Instead, the costs of interference apparently outweighed the benefits of extra food: female N. swarthi increased in mass with supplementary food, but female (relative to male) immigration and residency were repressed on all supplemented areas. This response supported the hypothesis of interference by aggressive encounter, and we were able to rule out the alternative hypotheses. Although periodic population crashes of R. rattus on the arid north coast of Santiago may ameliorate its competitive impact, climate change may tip the balance. Control or eradication of R. rattus should improve future survival prospects for N. swarthi, but wildlife managers must be prepared for the potential eruption of the introduced house mouse Mus musculus, because this species experienced a release from interference competition and immigrated to removal areas.

Hypothermia versus torpor in response to cold stress in the native Australian mouse Pseudomys hermannsburgensis and the introduced house mouse Mus musculus

This study compared torpor as a response to food deprivation and low ambient temperature for the introduced house mouse ( Mus musculus) and the Australian endemic sandy inland mouse ( Pseudomys hermannsburgensis). The house mouse (mass 13.0 ± 0.48 g) had a normothermic body temperature of 34.0 ± 0.20 °C at ambient temperatures from 5 °C to 30 °C and a basal metabolic rate at 30 °C of 2.29 ± 0.07 mL O 2 g − 1 h − 1 . It used torpor with spontaneous arousal at low ambient temperatures; body temperature during torpor was 20.5 ± 3.30 °C at 15 °C. The sandy inland mouse (mass 11.7 ± 0.16 g) had a normothermic T b of 33.0 ± 0.38 °C between T a of 5 °C to 30 °C, and a BMR of 1.45 ± 0.26 mL O 2 g − 1 h − 1 at 30 °C. They became hypothermic at low T a ( T b about 17.3 °C at T a = 15 °C), but did not spontaneously arouse. They did, however, survive and become normothermic if returned to room temperature (23 °C). We conclude that this is hypothermia, not torpor. Consequently, house mice (Subfamily Murinae) appear to use torpor as an energy conservation strategy whereas sandy inland mice (Subfamily Conilurinae) do not, but can survive hypothermia. This may reflect a general phylogenetic pattern of metabolic reduction in rodents. On the other hand, this may be related to differences in the social structure of house mice (solitary) and sandy inland mice (communal).

Introduced house mice Mus musculus: a significant predator of threatened and endemic birds on Gough Island, South Atlantic Ocean?

House mice Mus musculus have successfully colonized many temperate and sub-Antarctic islands that are the location for breeding colonies of millions of seabirds. Unlike other introduced mammals, the impact of house mice on seabirds and endemic birds is believed to have been negligible. The breeding ecology of seabirds breeding on Gough Island, central South Atlantic Ocean, was studied for the first time during September 2000 to September 2001. Breeding success of the endangered Tristan albatross Diomedea (exulans) dabbenena and endangered Atlantic Petrel Pterodroma incerta were 27.3 and 19.9% respectively. Mortality of large Tristan albatross and Atlantic petrel chicks was observed, and the pattern of wounds and observations of feeding indicate that introduced mice were responsible for this predation. Breeding numbers of the endemic Gough bunting Rowettia goughensis are mostly found in upland areas of Gough Island where mice are scarce and are restricted to inaccessible cliffs in the lowlands where mice are abundant. This pattern, together with the high predation rates of artificial-eggs in lowland habitats in comparison to the uplands, strongly suggests that mice constrain the distribution of Gough buntings. The results of this study provide the first evidence for the role of house mice as a significant predator of endangered and endemic birds. Further research is required to determine if the observed levels of mice predation are a regular occurrence.

Demography and conservation of the Tristan albatross Diomedea [exulans] dabbenena

The Tristan albatross Diomedea [exulans] dabbenena is the third rarest albatross species, with a breeding population of around 1500 pairs almost totally restricted to Gough Island in the Tristan da Cunha group, central South Atlantic. During January 2000, the entire breeding population of Gough was surveyed for the first time since 1956, and 2400 incubating pairs were counted. An analysis of the areas that are likely to have been surveyed most accurately in the past suggests that the population has decreased by around 28% over 46 years. The number of large chicks counted over three successive seasons (1999–2001) was highly variable (range 318–1129). The average count over this period (705 chicks) is less than counts made in 1979 (792) and 1982 (798). A total of 656 chicks were counted in September 2001, giving an island breeding success of just 27.3%. However, breeding success varied considerably in different areas of the island, ranging from 17.6 to 68.0%. During the 2001 season most breeding failures were of large chicks, and over 4 years where data were available, 75% of breeding failures occurred during the chick period. Predation by introduced house mice Mus musculus is the most likely cause of chick mortality. In a small study population, birds began breeding at an average age of 9.7 years and annual adult survival from 1985 to 2001 was 92.6% (SE=1.6%). Both breeding success and adult survival estimates are low in comparison with other Diomedea species and population modelling predicts a population decreasing at an annual rate of 2.9–5.3%. Further research is needed urgently to assess whether breeding success is typical, and to confirm that mouse predation is the cause of chick mortality. The low productivity of this species will compound the negative impacts of longline fishing mortality, which are likely to be reducing adult and juvenile survival.

Clearing and grazing impacts on vegetation patch structures and fauna counts in eucalypt woodland, Central Queensland

There is national and international concern that tree clearing and cattle grazing reduce habitat for native fauna. In this paper we quantify how the degree of clearing and the level of grazing change the patch structure and composition of vegetation in eucalypt woodlands, and how these habitat changes affect counts for 10 species including birds, reptiles and small mammals. These species were selected because they were abundant, hence providing the data needed for ordinations and regressions. We studied 37 sites occurring in two regions of central Queensland: Blackwater/Emerald and Alpha/Jericho. On each site, indices for the degree of tree clearing and the level of livestock grazing were assessed, the cover and size of tree groves, shrub thickets, log hummocks, termite mounds and perennial grass clumps were measured, and abundances of 10 common vertebrate species were estimated. As expected, the cover and size of tree groves declined and the cover of grass clumps increased as the degree of clearing increased. Native grass composition changed to introduced Buffel Grass as the level of grazing increased. Clearing affected fauna counts more than grazing did. The Grey Butcherbird Cracticus torquatus, Yellow-throated Miner Manorina flavigula, Striated Pardalote Pardalotus striatus and Pale-headed Rosella Platycercus eximius had significantly lower counts on cleared sites, but the Red-backed Fairy-wren Malurus melanocephalus had higher counts. The introduced House Mouse Mus musculus also had higher counts on cleared sites, but Carnaby's Skink Cryptoblephrus carnabyi had lower counts. Counts of the Weebill Smicrornis brevirostris, Bynoe's Gecko Heteronotia binoei and the Delicate Mouse Pseudomys delicatulus did not significantly change with clearing. Counts for the Pale-headed Rosella increased as the level of grazing increased, but counts for the other fauna species did not significantly change with our grazing index. Except for Bynoe's Gecko, fauna counts significantly changed with various vegetation patch attributes, particularly those strongly affected by clearing. From these results, we know which of the 10 fauna species are likely to decline or increase with clearing and grazing, and this knowledge can be used by land managers.