Bradford S. Keitt

Severity of the Effects of Invasive Rats on Seabirds : A Global Review

Invasive rats are some of the largest contributors to seabird extinction and endangerment worldwide. We conducted a meta-analysis of studies on seabird-rat interactions to examine which seabird phylogenetic, morphological, behavioral, and life history characteristics affect their susceptibility to invasive rats and to identify which rat species have had the largest impact on seabird mortality. We examined 94 manuscripts that demonstrated rat effects on seabirds. All studies combined resulted in 115 independent rat-seabird interactions on 61 islands or island chains with 75 species of seabirds in 10 families affected. Seabirds in the family Hydrobatidae and other small, burrow-nesting seabirds were most affected by invasive rats. Laridae and other large, ground-nesting seabirds were the least vulnerable to rats. Of the 3 species of invasive rats, Rattus rattus had the largest mean impact on seabirds followed by R. norvegicus and R. exulans; nevertheless, these differences were not statistically significant. Our findings should help managers and conservation practitioners prioritize selection of islands for rat eradication based on seabird life history traits, develop testable hypotheses for seabird response to rat eradication, provide justification for rat eradication campaigns, and identify suitable levels of response and prevention measures to rat invasion. Assessment of the effects of rats on seabirds can be improved by data derived from additional experimental studies, with emphasis on understudied seabird families such as Sulidae, Phalacrocoracidae, Spheniscidae, Fregatidae, Pelecanoididae, Phaethontidae, and Diomedeidae and evaluation of rat impacts in tropical regions.

Invasive mammal eradication on islands results in substantial conservation gains.

Significance Global conservation actions to prevent or slow extinctions and protect biodiversity are costly. However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions. Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species. This research quantifies the benefits to native island fauna of removing invasive mammals from islands. Our results highlight the importance of this conservation measure for protecting the worlds most threatened species. More than US

The diet of feral cats on islands: a review and a call for more studies

21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the worlds most imperiled fauna.

Eradicating multiple invasive species on inhabited islands: The next big step in island restoration?

Cats are among the most successful and damaging invaders on islands and a significant driver of extinction and endangerment. Better understanding of their ecology can improve effective management actions such as eradication. We reviewed 72 studies of insular feral cat diet from 40 islands worldwide. Cats fed on a wide range of species from large birds and medium sized mammals to small insects with at least 248 species consumed (27 mammals, 113 birds, 34 reptiles, 3 amphibians, 2 fish and 69 invertebrates). Three mammals, 29 birds and 3 reptiles recorded in the diet of cats are listed as threatened by the IUCN. However, a few species of introduced mammals were the most frequent prey, and on almost all islands mammals and birds contributed most of the daily food intake. Latitude was positively correlated with the predation of rabbits and negatively with the predation of reptiles and invertebrates. Distance from landmass was positively correlated with predation on birds and negatively correlated with the predation of reptiles. The broad range of taxa consumed by feral cats on islands suggests that they have the potential to impact almost any native species, even the smallest ones under several grams, that lack behavioral, morphological or life history adaptations to mammalian predators. Insular feral cat’s reliance on introduced mammals, which evolved with cat predation, suggests that on many islands, populations of native species have already been reduced.

High-impact Conservation: Invasive Mammal Eradications from the Islands of Western Mexico

Invasive species are the greatest threat to island ecosystems, which harbour nearly half the world’s endangered biodiversity. However, eradication is more feasible on islands than on continents. We present a global analysis of 1,224 successful eradications of invasive plants and animals on 808 islands. Most involve single vertebrate species on uninhabited islands, but plant and invertebrate eradications occur more often on inhabited islands. Inhabited islands are often highly modified and support numerous introduced species. Consequently, targeting a single invasive species can be ineffective or counterproductive. The impacts of other pests will continue and, in some cases, be exacerbated. The presence of people also creates regulatory, logistical and socio-political constraints. Real or perceived health risks to inhabitants, pets and livestock may restrict the use of some eradication tools, and communities or individuals sometimes oppose eradication. Despite such challenges, managing invasive species is vital to conserve and restore the unique biodiversity of many inhabited islands, and to maintain or improve the welfare and livelihoods of island residents. We present a brief case study of the Juan Fernández Archipelago, Chile, and discuss the feasibility of eradicating large suites of invasive plants and animals from inhabited islands while managing other invaders for which eradication is not feasible or desirable. Eradications must be planned to account for species interactions. Monitoring and contingency plans must detect and address any ‘surprise effects’. Above all, it is important that the local community derives social, cultural and/or economic benefits, and that people support and are engaged in the restoration effort.

Cat eradication significantly decreases shearwater mortality

Abstract Islands harbor a disproportionate amount of the earths biodiversity, but a significant portion has been lost due in large part to the impacts of invasive mammals. Fortunately, invasive mammals can be routinely removed from islands, providing a powerful tool to prevent extinctions and restore ecosystems. Given that invasive mammals are still present on more than 80% of the worlds major islands groups and remain a premier threat to the earths biodiversity, it is important to disseminate replicable, scaleable models to eradicate invasive mammals from islands. We report on a successful model from western México during the past decade. A collaborative effort between nongovernmental organizations, academic biologists, Mexican government agencies, and local individuals has resulted in major restoration efforts in three island archipelagos. Forty-two populations of invasive mammals have been eradicated from 26 islands. For a cost of USD 21 615 per colony and USD 49 370 per taxon, 201 seabird colonies and 88 endemic terrestrial taxa have been protected, respectively. These conservation successes are a result of an operational model with three main components: i) a tri-national collaboration that integrates research, prioritization, financing, public education, policy work, capacity building, conservation action, monitoring, and evaluation; ii) proactive and dedicated natural resource management agencies; and iii) effective partnerships with academic researchers in México and the United States. What is now needed is a detailed plan to eradicate invasive mammals from the remaining islands in the region that integrates the needed additional financing, capacity, technical advances, and policy issues. Island conservation in western México provides an effective approach that can be readily applied to other archipelagos where conservation efforts have been limited.

Albatross species demonstrate regional differences in North Pacific marine contamination

Introduced predators are a leading threat to seabird populations world-wide and cats ( Felis catus ) have probably had the most universally damaging effect (Moors & Atkinson, 1984). Eradication of feral cat populations from seabird colonies is a conservation priority (Tershy et al. , 2002) and there are many studies that demonstrate the benefits of these actions for seabirds (e.g. Forsell, 1982; Cooper et al. , 1995). However, detailed estimates of the effects of cat predation on seabird population viability are lacking in spite of the fact that such data could provide important support for land managers attempting to promote eradication programmes for seabird restoration.

Contaminant‐associated alteration of immune function in black‐footed albatross (Phoebastria nigripes), a North Pacific predator

Recent concern about negative effects on human health from elevated organochlorine and mercury concentrations in marine foods has highlighted the need to understand temporal and spatial patterns of marine pollution. Seabirds, long-lived pelagic predators with wide foraging ranges, can be used as indicators of regional contaminant patterns across large temporal and spatial scales. Here we evaluate contaminant levels, carbon and nitrogen stable isotope ratios, and satellite telemetry data from two sympatrically breeding North Pacific albatross species to demonstrate that (1) organochlorine and mercury contaminant levels are significantly higher in the California Current compared to levels in the high-latitude North Pacific and (2) levels of organochlorine contaminants in the North Pacific are increasing over time. Black-footed Albatrosses (Phoebastria nigripes) had 370-460% higher organochlorine (polychlorinated biphenyls [PCBs], dichlorodiphenyltrichloroethanes [DDTs]) and mercury body burdens than a closely related species, the Laysan Albatross (P. immutabilis), primarily due to regional segregation of their North Pacific foraging areas. PCBs (the sum of the individual PCB congeners analyzed) and DDE concentrations in both albatross species were 130-360% higher than concentrations measured a decade ago. Our results demonstrate dramatically high and increasing contaminant concentrations in the eastern North Pacific Ocean, a finding relevant to other marine predators, including humans.

ERADICATION OF NON-NATIVE MAMMALS AND THE STATUS OF INSULAR MAMMALS ON THE CALIFORNIA CHANNEL ISLANDS, USA, AND PACIFIC BAJA CALIFORNIA PENINSULA ISLANDS, MEXICO

Environmental pollution is ubiquitous and can pose a significant threat to wild populations through declines in fitness and population numbers. To elucidate the impact of marine pollution on a pelagic species, we assessed whether toxic contaminants accumulated in black-footed albatross (Phoebastria nigripes), a wide-ranging North Pacific predator, are correlated with altered physiological function. Blood samples from adult black-footed albatrosses on Midway Atoll, part of the Hawaiian (USA) archipelago, were analyzed for organochlorines (e.g., polychlorinated biphenyls [PCBs] and chlorinated pesticides), trace metals (silver, cadmium, tin, lead, chromium, nickel, copper, zinc, arsenic, selenium, and total mercury), and a sensitive physiological marker, peripheral white blood cell immune function (mitogen-induced lymphocyte proliferation and macrophage phagocytosis). We found a positive significant relationship between organochlorines, which were highly correlated within individual birds (p < 0.001, r > 0.80, Spearman correlation for all comparisons; PCBs, 160 +/- 60 ng/ml plasma [mean +/- standard deviation]; DDTs, 140 +/- 180 ng/ml plasma; chlordanes, 7.0 +/- 3.6 ng/ml plasma; hexachlorobenzene, 2.4 +/- 1.5 ng/ml plasma; n = 15) and increased lymphocyte proliferation (p = 0.020) as well as percentage lymphocytes (p = 0.033). Mercury was elevated in black-footed albatrosses (4,500 +/- 870 ng/ml whole blood, n = 15), and high mercury levels appeared to be associated (p = 0.017) with impaired macrophage phagocytosis. The associations we documented between multiple contaminant concentrations and immune function in endangered black-footed albatrosses provide some of the first evidence that albatrosses in the North Pacific may be affected by environmental contamination. Our results raise concern regarding detrimental health effects in pelagic predators exposed to persistent marine pollutants.

Reporting costs for invasive vertebrate eradications

Abstract The California Channel Islands, USA, and Pacific Baja California Peninsula Islands, Mexico (hereafter referred to as the California islands), are known for their high levels of biodiversity and globally important colonies of seabirds. We document the history, impacts, and management of non-native mammals and summarize the current status of native, non-volant mammals on the California islands. Of the 26 species of native mammals on the California islands, including 6 species and 41 subspecies that are endemic, ≥10 populations have suffered extirpation or global extinction. All recent extirpations and extinctions resulted directly from non-native mammalian predators or indirectly via habitat degradation by non-native herbivores. In light of the devastating effects non-native mammals have had on the native insular biotas of the California islands, a variety of organizations have collaborated to eradicate 44 populations of non-native mammals from 19 California islands. Documentation of impacts of non-native mammals and timely implementation of successful eradication efforts are essential to the conservation of these and other insular ecosystems.