Hawksbill turtles (Eretmochelys imbricata) are a circumtropical species that inhabit the waters of 108 countries, with nesting occurring in at least 70 of these [1]. They act as important transporters of nutrients across oceans [2] and promote biodiversity in coral reefs by consuming spatially competitive sponges [3]. Hawksbill turtles are listed as critically endangered and, along with six other sea turtle species, are included in the International Union for the Conservation of Nature Red List of Threatened Species [1].

Sea turtle populations are difficult to assess because of their complex life histories and migratory patterns. Global hawksbill turtle populations have demonstrated growth at targeted nesting sites in the past 20 years but an overall decline in numbers compared with historic levels (>20 to 100 years) [4]. Centuries of commercial exploitation for meat, eggs and tortoiseshell have led to diminishing populations that are further impacted by habitat destruction, pollution, climate change and fishing bycatch [1]. Population recovery is also hindered by the long maturation time (15–25 years) of the hawksbill turtle and the small proportion of hatchlings that survive until adulthood [5].

Conservation strategies that improve hatch success and hatchling survival are crucial to re-establishing healthy populations [6]. Previous strategies include the implementation of protective legislation, monitoring, nest safeguarding programmes, hatcheries and hatchling rehabilitation programmes [[7], [8], [9]]. Hawksbill turtles have an average hatch success of 78.6% [8]. Lower hatch success in other sea turtle species has been attributed to embryo mortality rather than infertility [10]. Extrinsic factors, such as temperature derangements, humidity and gaseous content, have been investigated as potential causes of mortality. Inundation, nest erosion and predation are significant contributors to embryo mortality but are typically excluded from calculations of hatch success.

Despite the significance of embryo mortalities in hatch success, pathology in perinatal sea turtles is poorly described and histopathological descriptions of sea turtle embryos are sparse. Malformations may be fatal to the developing embryo or impact its ability to hatch or emerge from the nest. In hawksbill turtles, malformations were observed in 41% of nests and 7.4% of embryos and were typically diagnosed in late-stage, unhatched eggs [11]. Mineralization, skeletal muscle necrosis, chorioallantoitis and bacterial pneumonia are some of the lesions reported in leatherback turtle (Dermochelys coriacea) embryos [12,13], but to the authors’ knowledge, comparable studies for hawksbill turtles are not available. Most (95%) hawksbill turtle hatchlings that die while in rehabilitative care have significant lesions, including anatomical malformations, dermatitis and pneumonia [14]. However, the prevalence of these lesions in turtles that do not successfully emerge from the nest is unknown as is the extent to which the occurrence of some of the lesions may be influenced by rehabilitation conditions.

The island nation of St. Kitts and Nevis acts as an important nesting area for the hawksbill turtle, leatherback turtle and green marine turtle (Chelonia mydas). The St. Kitts Sea Turtle Monitoring Network (SKSTMN) and the Nevis Turtle Group (NTG) are community-based organizations that monitor sea turtle populations and advocate for the conservation of sea turtles. These groups survey hawksbill turtle nesting grounds and excavate nests post emergence. Identifying the incidence and aetiologies of embryo mortality in hawksbill turtles is vital to the repopulation of this critically endangered species. The objective of this study was to describe the mortality and pathology of hawksbill turtle embryos and dead-in-nest hatchlings from St. Kitts and Nevis and identify any lesions that could contribute to perinatal mortality.