Prevalence of visible injuries to leatherback sea turtles Dermochelys coriacea in the Northwest Atlantic

Abstract

Identification and understanding of various patterns of injury in marine species such as cetaceans and sea turtles can elucidate corresponding threats and inform conservation efforts.Here we used standardized external injury assessments to investigate the relative importance of direct anthropogenic and natural threats to the Northwest Atlantic population of leatherback turtles Dermochelys coriacea, and to evaluate whether susceptibility to these threats varies between low-latitude nesting and high-latitude foraging regions, and by sex and size (i.e. age). We sampled leatherbacks foraging in temperate waters off Nova Scotia, Canada (n = 92), and at a nesting beach in Trinidad, West Indies (n = 137), where, combined, 62% of turtles exhibited characteristic markings associated with at least 1 injury (i.e. entanglement scarring, amputations, bites, etc.). There were no significant differences in injury rate or type between regions or between sexes or size classes. The proportion of leatherbacks exhibiting injuries of suspected anthropogenic origin (34%) was significantly higher (p < 0.001) than the proportion with injuries of suspected predatory origin (16%), but did not exceed the proportion with injuries of unknown origin (34%). Nineteen percent exhibited injuries indicative of entanglement in rope, lines, or nets, and 17% showed evidence of potential interaction with hooks. These results suggest that the Northwest Atlantic leather back population faces common and possibly widely distributed threats from both predators and fishing gear across its range and are consistent with growing evidence positing fisheries bycatch as one of the principal direct threats facing this species.

Evaluating prevalence of external injuries on nesting loggerhead sea turtles Caretta caretta in southeastern Florida, USA

“…Loggerhead sea turtles have relatively accurate target biting, which results in greater hooking in the mouth, throat, and stomach (Epperly et al 2012, Warraich et al 2020; therefore small pieces of the maxilla that were missing were categorized as hook injuries. Injuries were categorized as entanglement if lacerations encircled the neck or appendage or if gear (which was removed from the animal during oviposition) was still present on the turtle (Innis et al 2010, Archibald & James 2018. Fresh injuries were defined as those with open wounds with blood present and the absence of scarring tissue.…”

“…Loggerheads often have a greater prevalence of shark bite injuries in comparison to green turtles Chelonia mydas, as they swim at slower speeds and have less maneuverability (Heithaus et al 2002). Compared to predator attacks, anthropogenic injuries in northwestern Atlantic leatherback sea turtles Dermochelys coriacea are twice as common (Archibald & James 2018).…”

Sublethal Injuries and Physical Abnormalities in Maldives Manta Rays, Mobula alfredi and Mobula birostris

“…Assessment of the origins of sublethal injury to individuals provides a method for investigating the relative impact of different types of threats to a species (Archibald and James, 2018). Researchers have investigated sublethal injuries to M. alfredi in Mozambique, Hawaii, French Polynesia, Australia, and Indonesia (Marshall and Bennett, 2010;Deakos et al, 2011;Carpentier et al, 2019;Germanov et al, 2019;McGregor et al, 2019), and to M. birostris in southeast Florida, United States (Pate and Marshall, 2020).…”

Examining shark bite scars on dolphins off Bimini, The Bahamas: Comparisons between bottlenose and Atlantic spotted dolphins

“…Estimating failed predation attempts, through the documentation of injuries and scars attributed to sharks, can be used to infer predation pressure on dolphins. This approach is not exclusive to small cetaceans, e.g., it has been applied to manta rays (Manta alfredi; Marshall & Bennett, 2010), green (Chelonia mydas) and loggerhead sea turtles (Caretta caretta; , and leatherback sea turtles (Dermochelys coriacea; Archibald & James, 2018). Among dolphins, it has most commonly been used with well-studied populations of bottlenose dolphins (Tursiops aduncus; Corkeron et al, 1987a;Heithaus, 2001b;Heithaus et al, 2017;Sprogis et al, 2018;T.…”

“…Estimating failed predation attempts, through the documentation of injuries and scars attributed to sharks, can be used to infer predation pressure on dolphins. This approach is not exclusive to small cetaceans, e.g., it has been applied to manta rays ( Manta alfredi ; Marshall & Bennett, 2010), green ( Chelonia mydas ) and loggerhead sea turtles ( Caretta caretta ; Heithaus et al, 2002), and leatherback sea turtles ( Dermochelys coriacea ; Archibald & James, 2018). Among dolphins, it has most commonly been used with well‐studied populations of bottlenose dolphins ( Tursiops aduncus ; Corkeron et al, 1987a; Heithaus, 2001b; Heithaus et al, 2017; Sprogis et al, 2018; T. truncatus ; Wilkinson et al, 2017), but also Australian snubfin ( Orcaella heinsohni ) and Australian humpback dolphins ( Sousa sahulensis ; Smith et al, 2018), Guiana dolphins ( Sotalia guianensis ; Santos & Gadig, 2009), and Atlantic spotted dolphins ( Stenella frontalis ; Melillo‐Sweeting et al, 2014).…”