Predation on endangered species by human-subsidized domestic cats on Tokunoshima Island

Role of landscape context in Toxoplasma gondii infection of invasive definitive and intermediate hosts on a World Heritage Island

Free-ranging cats are invasive species threatening biodiversity worldwide. They may also impose an environmental risk to humans and livestock through the transmission of zoonotic diseases. We investigated antibody levels against Toxoplasma gondii in free-ranging cats and black rats (definitive and representative intermediate hosts) by ELISA and determined their relationships with landscape environmental factors on Tokunoshima Island, Japan, the Natural World Heritage site. We found a higher seroprevalence (>70%) in both cats and black rats in landscapes where the cattle barn density was high. This was consistent with higher density of rats revealed in our trapping survey. The spatial scale of landscape factors affecting infection was broader in cats (1 km buffer radius) than in black rats (100 m buffer radius). Both cats and rats showed an increasing trend in optical density (OD) values with increasing body weight and landscape cattle barn density, suggesting that the antibody concentration increases as the chance of exposure to T. gondii in the environment increases. Thus, management actions to stop humans from feeding cats and to control rat populations without using cats are both necessary to reduce the human health risk as well as to conserve endangered species on the island.

•

High seroprevalence of T. gondii was found in cats and black rats on an island.

•

Seroprevalence was high (>70%) in landscapes where there were many cattle barns.

•

Antibody level in cats was lower in forests and higher around residential areas.

•

Spatial scale of environmental factors affecting infection was broader in cats.

Stable isotopes unveil one millennium of domestic cat paleoecology in Europe

The domestic cat is the world's most popular pet and one of the most detrimental predators in terrestrial ecosystems. Effective protection of wildlife biodiversity demands detailed tracking of cat trophic ecology, and stable isotopes serve as a powerful proxy in dietary studies. However, a variable diet can make an isotopic pattern unreadable in opportunistic predators. To evaluate the usefulness of the isotopic method in cat ecology, we measured C and N isotope ratios in hundreds of archaeological cat bones. We determined trends in cat trophic paleoecology in northern Europe by exploiting population-scale patterns in animals from diverse locations. Our dataset shows a high variability of isotopic signals related to the socio-economic and/or geomorphological context. This points toward regularities in isotopic patterns across past cat populations. We provide a generalized guide to interpret the isotopic ecology of cats, emphasizing that regional isotopic baselines have a major impact on the isotopic signal.

Strigolactones (SLs) modulate the plastochron by regulating KLUH (KLU) transcript abundance in Arabidopsis

The timing of leaf emergence at the shoot apical meristem, or plastochron, is highly regulated in plants. Among the genes known to regulate the plastochron in Arabidopsis (Arabidopsis thaliana), KLUH (KLU), orthologous to the rice (Oryza sativa) PLASTOCHRON1, encodes the cytochrome P450 CYP78A5, and is thought to act through generation of a still unknown mobile signal. As klu mutants display not only a short plastochron but also a branching phenotype reminiscent of strigolactone (SL) mutants, we investigated whether KLU/CYP78A5 is involved in SL biosynthesis. We combined a genetic approach, a parasitic plant seed germination bioassay to test klu root exudates, and analysis of transcript abundances of SL-biosynthesis genes in the Arabidopsis klu mutants. We demonstrate that KLU is not involved in the SL-biosynthesis pathway. Moreover, this work allowed us to uncover a new role for SL during Arabidopsis development in modulating plastochron via a KLU-dependent pathway. Globally our data reveal that KLU is required for plastochron-specific SL responses, a first indication of crosstalk between SL and the KLU-derived signal.

Use of molecular scatology to assess the diet of feral cats living in urban colonies

The overpopulation of domestic cats (Felis catus) presents a serious concern for wildlife conservationists, animal welfare advocates, public health officials, and community members alike. In cities, free-ranging, unowned cats often form high-density groups (commonly called ‘colonies’) around human provisioned food sources. While previous diet studies have primarily utilized morphology-based methods, molecular techniques offer a higher resolution alternative. In this study, we used next-generation sequencing techniques to examine the diet composition of feral cats living in five Trap-Neuter-Return colonies located in urban parks on Staten Island, a borough of New York City. We hypothesized that (1) cats living in urban colonies would still consume natural prey despite being regularly fed and (2) that the composition of taxa represented in the diet of each colony would vary, possibly due to differences in prey availability across sites. In total, 16 vertebrate prey taxa were identified in the diet, 13 at the genus level and 3 at the family level. Despite being regularly fed, 58.2% of cat scats contained DNA from natural prey. The diet composition of the cat colonies differed depending on the land cover composition surrounding the colony with the frequency of native prey positively correlated with the proportion of green space and that of non-native prey with developed land cover types. The use of molecular techniques combined with environmental DNA methods offers a promising, non-invasive approach to assessing the diet and consequently, impact of a highly abundant and non-native predator on the persistence of wildlife communities in cities.

Spatial distribution of anti-Toxoplasma gondii antibody-positive wild boars in Gifu Prefecture, Japan

Toxoplasma gondii is a globally wide-spread parasite that infects almost all species of mammals and birds, including humans. We studied the spatial distribution of individual T. gondii-seropositive wild boar in Gifu Prefecture (10,621 km²), Japan. Altogether, 744 wild boars were captured at 663 points around human settlements in Gifu Prefecture. Serum samples were collected after recording the exact capture locations, along with each wild boar’s body length and sex. We then used a commercial enzyme-linked immunosorbent assay kit for swine to measure anti-T. gondii antibodies in these animals. Among the 744 wild boars, 169 tested positive for T. gondii (22.7%). No significant difference in T. gondii seroprevalence was observed between the mountainous northern region with high winter snow cover and the mild-wintered geographical plain of the southern part of the prefecture. In contrast, 8 of the 11 wild boars that were captured in a public park surrounded by residential areas showed T. gondii seropositivity (72.7%), a value significantly higher than those of the wild boar populations in the other prefecture areas. This in-depth analysis, which spans the big city suburbs and rural areas of a whole prefecture, explains the seroprevalence of zoonotic T. gondii in wild boar and has public health implications.

First synthesis of the economic costs of biological invasions in Japan

Despite the large body of knowledge recognising the impact of biological invasions on biodiversity, their economic impact has been less evaluated. However, the associated economic costs ought to provide useful information on many different aspects to prevent and manage invasions. Here, we describe the economic costs of biological invasions in Japan using InvaCost, a recently-published global database on monetary costs extracted from English and non-English sources, as well as a complementary search, thereby filling a gap in regional knowledge. We focused on the following four dimensions when analysing the economic costs of biological invasions: damage to biodiversity, damage to human livelihood, management for biodiversity and management for human livelihood. Interestingly, there was no information about biological invasion costs for Japan in English, but the Japanese search and our additional survey provided a total of 630 cost entries, with a total economic cost of 728 million USD (2017 value, equivalent to 62 billion JPY). These entries appeared in 33 documents and corresponded to a total of 54 species. We showed that: 1) damage costs from biological invasions tend not to be assessed as frequently as management costs and are more underestimated; 2) despite the numerous entries, an overwhelmingly limited amount of the management budget was allocated to biodiversity conservation compared to protecting human livelihood; 3) budgets have been intensively invested in invasive species management on small islands, which reflects the vulnerability of small island ecosystems and economies to biological invasions; 4) the recorded costs still seem to be greatly underestimated, mainly due to the lack of recording (and potentially limited access to recorded cost information). These findings are not only specific to Japan, but may also be widely applicable to most other countries. The future recording of economic costs will help to close the gap between actual and recorded costs, leading to more realistic guidelines for tackling biological invasions.

The Role of Pathogen Dynamics and Immune Gene Expression in the Survival of Feral Honey Bees

Studies of the ecoimmunology of feral organisms can provide valuable insight into how host–pathogen dynamics change as organisms transition from human-managed conditions back into the wild. Honey bees (Apis mellifera Linnaeus) offer an ideal system to investigate these questions as colonies of these social insects often escape management and establish in the wild. While managed honey bee colonies have low probability of survival in the absence of disease treatments, feral colonies commonly survive in the wild, where pathogen pressures are expected to be higher due to the absence of disease treatments. Here, we investigate the role of pathogen infections [Deformed wing virus (DWV), Black queen cell virus (BQCV), and Nosema ceranae] and immune gene expression (defensin-1, hymenoptaecin, pgrp-lc, pgrp-s2, argonaute-2, vago) in the survival of feral and managed honey bee colonies. We surveyed a total of 25 pairs of feral and managed colonies over a 2-year period (2017–2018), recorded overwintering survival, and measured pathogen levels and immune gene expression using quantitative polymerase chain reaction (qPCR). Our results showed that feral colonies had higher levels of DWV but it was variable over time compared to managed colonies. Higher pathogen levels were associated with increased immune gene expression, with feral colonies showing higher expression in five out of the six examined immune genes for at least one sampling period. Further analysis revealed that differential expression of the genes hymenoptaecin and vago increased the odds of overwintering survival in managed and feral colonies. Our results revealed that feral colonies express immune genes at higher levels in response to high pathogen burdens, providing evidence for the role of feralization in altering pathogen landscapes and host immune responses.

Prevalence of serum antibodies to Toxoplasma gondii in free-ranging cats on Tokunoshima Island, Japan

The prevalence of Toxoplasma gondii infection in free-ranging cats on Tokunoshima Island was assessed by testing 125 serum samples using anti-T. gondii IgG indirect enzyme-linked immunosorbent assay. The overall seropositivity rate was 47.2% (59/125). Seropositivity rates in cats with body weight >2.0 kg (57.4%) were significantly higher than in those with body weight ≤2.0 kg (12.5%, P<0.01). Analysis of the number of seropositive cats by settlement revealed the presence of possibly-infected cats in 17 of 23 settlements, indicating the widespread prevalence of T. gondii on the island. This is the first study to show the seroprevalence of T. gondii in free-ranging cats on Tokunoshima Island. The information revealed in this paper will help to prevent the transmission of T. gondii among cats and also in both wild and domestic animals and humans on the island.

Identification of the population source of free-ranging cats threatening endemic species on Tokunoshima Island, Japan

Free-ranging cats Felis silvestris catus are harmful to endemic species, especially on islands. Effective management practices require an understanding of their habitat use and population source at the landscape level. We aimed to identify the source of the free-ranging cat population on Tokunoshima Island, Japan, which harbors a variety of endemic organisms as well as human settlements. Trapping data for the whole island were provided by local governments, and landscape factors (residential, agricultural, and woodlot areas and cattle barn density) affecting cat density were explored. An analysis of live-capture data indicated that the density (per 1 km2) of free-ranging cats was positively correlated with the densities of cattle barns and woodlot areas and negatively correlated with residential areas. An interview survey revealed that nearly half of the cattle barns feed free-ranging cats. The source habitat of free-ranging cats appears to be areas with a high density of cattle barns and a high percentage of woodlots in human-dominated landscapes. Feeding cats in cattle barns may strengthen the bottom-up process of population growth on the island. To reduce the impact of cats on endemic species on Tokunoshima Island, efforts to stop feeding cats in cattle barns are important. Reaching a consensus with stakeholders will require further studies of the ecological risks posed by free-ranging cats.