Ecological release and insular shifts in avian morphological traits in the Caribbean

We compared support for 3 hypotheses that might explain observed morphological variation among islands of 4 species of Caribbean land birds: ecological release from competition and predation pressure, predation pressure from 1 novel predator species (small Indian mongoose, Herpestes auropunctatus), and climate. We measured wing chord, tarsus length, bill length, and mass of Bananaquits (Coereba flaveola), Black-faced Grassquits (Tiaris bicolor), Lesser Antillean Bullfinches (Loxigilla noctis), and Common Ground Doves (Columbina passerina) in Grenada, 2015–2017, and combined these measures with data from 23 other Caribbean islands collated from academic papers and researchers, for a total sample size of 6,518 individuals. We found the strongest support for the ecological release hypothesis, but each of our hypotheses received some support, suggesting that ecological release from competition, predation pressure from mongoose, and climate may all interact to influence morphological adaptations of birds to local conditions in the Caribbean.

Reintroducing species when threats still exist: assessing the suitability of contemporary landscapes for island endemics

Reintroducing species into landscapes with persistent threats is a conservation challenge. Although historic threats may not be eliminated, they should be understood in the context of contemporary landscapes. Regenerating landscapes often contain newly emergent habitat, creating opportunities for reintroductions. The Endangered St Croix ground lizard Pholidoscelis polops was extirpated from the main island of St Croix, U.S. Virgin Islands, as a result of habitat conversion to agriculture and predation by the small Indian mongoose Herpestes auropunctatus. The species survived on two small cays and was later translocated to two islands. Since the 1950s, new land-cover types have emerged on St Croix, creating a matrix of suitable habitat throughout the island. Here we examined whether the new habitat is sufficient for a successful reintroduction of the St Croix ground lizard, utilizing three complementary approaches. Firstly, we compared a map from 1750 to the current landscape of St Croix and found statistical similarity of land-cover types. Secondly, we determined habitat suitability based on a binomial mixture population model developed as part of the programme monitoring the largest extant population of the St Croix ground lizard. We estimated the habitat to be sufficient for > 142,000 lizards to inhabit St Croix. Thirdly, we prioritized potential reintroduction sites and planned for reintroductions to take place during 2020–2023. Our case study demonstrates how changing landscapes alter the spatial configuration of threats to species, which can create opportunities for reintroduction. Presuming that areas of degraded habitat may never again be habitable could fail to consider how regenerating landscapes can support species recovery. When contemporary landscapes are taken into account, opportunities for reintroducing threatened species can emerge.

First Report on Detection and Genetic Diversity of Picobirnaviruses in the Small Indian Mongoose (Herpestes auropunctatus)

Picobirnaviruses (PBVs), family Picobirnaviridae, are bi-segmented, double-stranded RNA viruses. PBVs are considered opportunistic enteric pathogens. Gene segment-1 of PBV encodes the capsid protein, whilst gene segment-2 codes for RNA-dependent RNA polymerase (RdRp). Based on differences in gene segment-2, PBVs are classified into genogroup-I (GI) and GII. Although PBVs have been detected in a wide variety of host species, there are no reports on PBVs from mongoose so far. We report here high rates of detection (35.36%, 29/82) of GI PBVs in fecal samples from the small Indian mongoose (Herpestes auropunctatus) on the Caribbean island of St. Kitts. Applying a combination of a non-specific primer-based amplification method and conventional RT-PCR using a newly designed primer targeting the 3′-untranslated region (UTR), we could amplify and sequence the complete/nearly complete gene segment-2 of eight mongoose PBV strains. Except for a single strain, the gene segment-2 of the remaining mongoose PBV strains contained the putative open reading frame encoding the RdRp. The gene segment-2/putative RdRps of the mongoose PBV strains retained various features that are conserved in other PBVs (5′- and 3′-terminal nucleotide sequences, bacterial ribosomal binding site sequence in 5′-UTR, and the three domains in putative RdRps). On the other hand, phylogenetic analysis and sequence identities of the putative RdRps revealed high genetic diversity among the mongoose PBV strains and with those of PBVs from other host species. To our knowledge, this is the first report on detection and genetic diversity of PBVs from the mongoose, expanding the host range of PBVs and providing vital insights into the various features and evolution of putative RdRps of PBVs in a new host species.

Chemosensory deficiency may render island-dwelling lizards more vulnerable to invasive predators

Newly introduced predators constitute a major threat to prey populations worldwide. Insular prey animals in particular often do not succeed in overcoming their naivety towards alien predators, making them specifically vulnerable. Why this is the case remains incompletely understood. Here, we investigate how the ability to detect and respond to predator chemical cues varies among populations of the Dalmatian wall lizard, Podarcis melisellensis. Lizards were sampled from five locations in south-eastern Croatia (one mainland location and four islands) that varied in the composition of their predator community. We observed the lizards’ behaviour in response to chemical cues of native saurophagous snakes (the Balkan whip snake, Hierophis gemonensis, and eastern Montpellier snake, Malpolon insignitus) and an introduced mammalian predator (the small Indian mongoose, Herpestes auropunctatus – a species held responsible for the loss of numerous insular reptile populations worldwide). Mainland lizards showed elevated tongue-flick rates (indicative of scent detection) as well as behaviours associated with distress in response to scents of both native and introduced predators. In sharp contrast, island lizards did not alter their behaviour when confronted with any of the predator cues. Alarmingly, even lizards from islands with native predators (both snakes and mammals) and from an island on which mongooses were introduced during the 1920s were non-responsive. This suggests that insular populations are chemosensorily deprived. As failure at the predator-detection level is often seen as the most damaging form of naivety, these results provide further insight into the mechanisms that render insular-living animals vulnerable to invasive species.

Mongoose (Herpestes auropunctatus) May Not Be Reservoir Hosts for Mycobacterium bovis in Fiji Despite High Population Density and Direct Contact with Cattle

The presence of a wildlife reservoir for Mycobacterium bovis complicates the eradication of bovine tuberculosis (BTB) from domestic cattle populations. For the BTB eradication program in Fiji, there is concern about the small Indian mongoose (Herpestes auropunctatus), which is overabundant and in direct contact with cattle. Consequently, a survey of mongooses trapped on three BTB affected dairy farms led to necropsy of 85 mongooses during January–February 2017. Thirty (35%) mongooses had gross pathological changes including possible granulomas detected at necropsy, and tissues from these animals were taken for histopathological examination. Granulomatous lesions were present in 53% of animals examined histopathologically but acid-fast bacilli were not observed and the majority of lesions in lung and kidney were associated with the nematodes Pulmostrongylus herpestis and Capillaria sp., respectively. Nevertheless, assuming test sensitivity of 35% for the current study, from this sample of 85 mongooses it can be concluded with 95% confidence that if present in the mongoose population susceptible to trapping, M. bovis prevalence was ≤10%. The prevalence of intercurrent lesions raised concerns about gross pathology as a screening test for M. bovis infection in mongooses in Fiji, and therefore pathogen detection methods such as bacterial culture and direct tissue PCR are recommended for future surveys. These are needed to completely rule out the mongoose as a reservoir host for M. bovis in Fiji.