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Figure 1. Map of the Pacific Northwest of Costa Rica including the location where both the fork (this study) and the straw (Robinson & Figgener 2015) were removed from an olive ridley turtle.

We encountered the olive ridley turtle at Ostional beach on the Pacific coast of Costa Rica (9° 56’, 85° 39’, Fig. 1). Playa Ostional hosts sea turtle mass-nesting events, termed arribadas. We were present during one such arribada on 6 December 2015 to collect epibionts from nesting olive ridley turtles. While conducting our research, we were alerted about a nesting olive ridley turtle that had a foreign body protruding approximately 4 cm from its right nostril (Fig. 2a). Having immediate concerns for the turtle’s health, as the foreign body was likely impairing the turtle’s ability to breathe, we attempted to gently remove the foreign body.

Figure 2. (A) Plastic fork in the right nostril of an olive ridley sea turtle. (B) Removal of the fork. (C) The fork next to a ruler for scale.

The foreign body appeared firmly lodged in place; however, bringing the turtle in for veterinary treatment was not an option. It would take many hours to drive to the nearest veterinary clinic and we had no assurance that appropriate treatment would be available. In addition, moving the animal would have been in violation of our permits, which only allowed us to restrain the turtle for a maximum of 20 min - the time required to exhaustively collect epibionts from a nesting sea turtle. Thus, we decided to remove the it in situ.

We firmly gripped on the protruding end of the foreign body with a Swiss Army knife. After a short pull, the object came free from the turtle’s nose (Fig. 2b). Upon removal, we discovered that the foreign body was a plastic fork. The fork measured 13 cm long (Fig. 2c), and approximately 9 cm of the fork, including the tines, had been inside the sea turtle’s nasal passage before removal. After the fork was removed, the turtle appeared healthy and it crawled back to the ocean and swam away.

This is the second report of a plastic foreign body in the nostril of a sea turtle, the first being a plastic straw (Robinson & Figgener 2015). Interestingly, the straw was discovered nearby in the waters in front of Playas Del Coco only five months previous (Fig. 1; approx. 60 km north of Playa Ostional) and it also affected an olive ridley turtle. The occurrence of two such events in close proximity within a short time frame could be attributable to increased surveillance effort. Indeed, both the straw and the fork were discovered as part of the same study on epibiont diversity that began in 2014 and requires us to closely inspect sea turtles for epibionts. However, scientists have been monitoring nesting olive ridley sea turtles along the Pacific coast of Costa Rica for many years (e.g., Fonseca et al. 2009; Valverde et al. 2012; Dornfeld et al. 2015) and such an event had not previously been recorded. Thus, increased surveillance alone is unlikely to explain these recent discoveries. Instead, we consider that these recent discoveries are the product of accumulating plastic debris in the waters of northwest Costa Rica. Increased quantities of plastic debris could be attributed to either the steady increase in plastic pollution from local sources (e.g., riverine input) or dynamic oceanographic processes that may lead to local aggregations of plastic debris from potentially distant sources (Duhec et al. 2015).

The direction that the fork was pointing may provide some crucial insights as to how the fork came to be found within the turtle’s nose. As the fork was found with the tines pointed posteriorly into the turtle’s nasal passage, it is highly unlikely that the fork could have entered the external nares by force. Instead, we hypothesize that the turtle first ingested the plastic fork and then tried to regurgitate it. Sea turtles regularly ingest plastic objects (Schuyler et al. 2014; Nelms et al. 2015; Wedemeyer-Strombel et al. 2015), presumably after mistaking them for prey items (Schuyler et al. 2012). A plastic fork could have been mistaken for a penaeid shrimp or a crab’s appendage - both prey items that are regularly found in the stomachs of olive ridley turtles (Colman et al. 2014). Being rigid, the fork was angled toward the roof of the mouth as it was regurgitated. Instead of passing out of the mouth, the fork was consequently passed into the internal nares, which are found on the roof of the mouth (Fig. 3, from Wyneken 2001). Moreover, the width of the fork’s head stopped the fork from being passing completely out of the nasal passage. This pattern of ingestion and regurgitation is also probably the most parsimonious explanation for how a straw came to be lodged in a sea turtle’s nostril (Robinson & Figgener 2015).

Figure 3. Dorsal and ventral perspectives of an olive ridley sea turtle’s skull indicating the position of the external and internal nares. Modified from Wyneken 2001.

While it is often assumed that sea turtles are unable to regurgitate items due to the presence of esophageal papillae (Magalhães et al. 2012, Schuyler et al. 2014), this is not entirely correct. Sea turtles have regularly been observed to regurgitate partially liquefied foods after being tube fed or receiving a gastric-esophageal lavage (Mendonça 1983; Norton 2005). As turtles can therefore exhibit a regurgitation response, it might therefore be possible for turtles to occasionally regurgitate solid items, such as a plastic fork or straw. This might be especially true if the solid item has only passed as far as the pharynx and not the esophagus. If this is true, and we also consider the quantity of plastic that might pass naturally through the alimentary canal, the quantity of plastic debris found in the stomach of sea turtles is probably an underestimation of the total plastic that these animals ingest over their lives.

Considering that studies are now reporting plastics present in the stomachs of over 80% of turtles sampled (Schuyler et al. 2014; Wedemeyer-Strombel et al. 2015), many turtles worldwide are likely to have some form of interaction with plastic debris over their life time. Although the full extent of the threat that pollution poses to sea turtles, or most marine life, is still largely unknown (Rochman et al. 2016), the overwhelming prevalence of plastic debris in the guts of marine animals is a worrying sign. We predict that over time, methods for reducing plastic pollution on a global scale are likely to play an increasingly necessary role in conservation management strategies for many endangered marine species.

Acknowledgements. This research was conducted under permits from SINAC (#ACT-OR-DR-099-15). We thank Roberto Zúñiga Muños and the Area de Conservación Tempisque for their support of research. We thank Victoronix for providing essential equipment for this study. Pilar Santidrián Tomillo provided assistance with permitting. Yeudy José Arguello Gómez helped coordinate logistics at Playa Ostional.

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