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

Abstract

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.

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

“…The high antibody levels in both cats and black rats in areas with many cattle barns suggest that cattle barns are a hotspot for the maintenance of a high frequency of T. gondii infections on Tokunoshima Island. This is consistent with an earlier study showing that the cat density is high in areas with a high barn density on this island ( Kazato et al, 2020 ), which probably caused substantial oocyst shedding by cats in these areas. The high antibody levels and high prevalence of antibodies to T. gondii in black rats strongly suggest that T. gondii spills over from cats to intermediate hosts via environmental sources, such as soil and water.…”

“…With respect to land use variables, we expected higher infection levels in cats in areas where green space is abundant, where they show a higher density on Tokunoshima Island ( Kazato et al, 2020 ). However, antibody levels were actually lower in areas with more forests and higher around residential areas, as indicated by the negative effect of PC1.…”

“…There are three possible explanations for the higher seroprevalence in black rats than in cats, which are not mutually exclusive. First, cats around cattle barns may be well-fed by farmers ( Kazato et al, 2020 ; Qi et al, 2022 ) and therefore rarely consume black rats, implying that the infection route through intermediate hosts is weakened and the cat seroprevalence may remain low ( Afonso et al, 2006 ). Second, the difference in seroprevalence may be due to the difference in home range sizes between the two animal species.…”

“…More specifically, cattle barns were found to be a hot spot for T. gondii infection in both definitive and intermediate hosts. The high density of cats benefiting from feeding cats by farmers can explain this high infection rate ( Kazato et al, 2020 ). Efforts to stop feeding outdoor cats may thus reduce the risk of infection by reducing the cat abundance.…”

“…Beef cattle production is also common; there are about 1000 beef cattle barns, with 9.6 breeding cattle per household, on average ( Agriculture, 2019 ). Cats are often kept outside around barns with the main purpose of controlling black rats ( Kazato et al, 2020 ; Qi et al, 2022 ), which are believed to attract venomous snakes ( Protobothrops flavoviridis ), a threat to residents. A questionnaire survey revealed that cats are fed by humans in 45% of barns on the island ( Kazato et al, 2020 ).…”