Mouse eradication is required to prevent local extinction of an endangered seabird on an oceanic island

Abstract

Petrels (Procellariidae) are a highly diverse family of seabirds, many of which are globally threatened due to the impact of invasive species on breeding populations. While predation by invasive cats and rats has led to the extinction of petrel populations, the impact of invasive house mice Mus musculus is slower and less well documented. However, mice impact small burrow-nesting species such as MacGillivray’s prion Pachyptila macgillivrayi, a species classified as endangered because it has been extirpated on islands in the Indian Ocean by introduced rodents. We use historic abundance data and demographic monitoring data from 2014 to 2020 to predict the population trajectory of MacGillivray’s prion on Gough Island with and without a mouse eradication using a stochastic integrated population model. Given very low annual breeding success (0.01 fledglings per breeding pair in ‘poor’ years (83%) or 0.38 in ‘good’ years (17%), n = 320 nests over 6 years) mainly due to mouse predation, our model predicted that the population collapsed from ~3.5 million pairs in 1956 to an estimated 175,000 pairs in 2020 despite reasonably high adult survival probability (ϕ = 0.901). Based on these parameters, the population is predicted to decline at a rate of 9% per year over the next 36 years without a mouse eradication, with a 31% probability that by 2057 the MacGillivray’ prion population would become extremely vulnerable to extinction. Our models predict population stability (λ = 1.01) and a lower extinction risk (<10%) if mouse eradication on Gough Island restores annual breeding success to 0.519, which is in line with that of closely-related species on predator-free islands. This study demonstrates the devastating impacts that introduced house mice can have on small burrowing petrels and highlights the urgency to eradicate invasive mammals from oceanic islands.

Independent evolution of intermediate bill widths in a seabird clade

“…Given that the relict P. macgillivrayi population in the Indian Ocean is very small, our results demonstrating that the newly discovered medium-billed prions population on Gough corresponds to a new population of MacGillivray’s prion are of utmost relevance for the conservation of this species. Our results provide further evidence for the need to eradicate introduced house mice from Gough Island (Holmes et al 2019 ; Jones et al 2021 ).…”

“…If so, it also qualifies as Endangered under Criterion B2b. The recognition of yet another globally threatened species that is virtually confined to Gough Island provides further impetus for the need to eradicate mice from the island (Jones et al 2021 ).…”

Cryptic population decrease due to invasive species predation in a long‐lived seabird supports need for eradication

“…Procellariiformes (albatrosses and petrels) have the longest time periods between fledging and maturity amongst seabirds (5–15 years; Ricklefs, 1990; Brooke, 2004), and many albatrosses do not attempt to breed in the year after raising a chick, further increasing the number of individuals that are not observable at the breeding colony (Carneiro et al, 2020; Pardo et al, 2013). Consequently, annual counts of breeding pairs, or individuals at the colony, may not immediately reflect the impact that invasive non‐native species can have on seabird population dynamics, and an observable population response following either the introduction or the successful eradication of invasive species may take decades (Jones, 2010; Jones et al, 2021).…”