HOLDING AND HEADSTARTING SEA TURTLE HATCHLINGS
ANDREA D. PHILLOTT
FLAME University, Pune, Maharashtra, India
andrea.phillott@gmail.com
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INTRODUCTION
Human actions which intervene in the natural life history of sea turtles can significantly impact their survival. For this reason, it has been previously recommended that hatcheries use evidence-based practices for egg collection, transport and incubation that consider the vulnerability and required environment of the embryo inside the egg (e.g., Phillott & Shanker, 2018). Similarly, the care and release of hatchlings after emergence from the nest should also be based on their biology and behaviour.
Growing concerns about hatchery practices, including the holding of sea turtle hatchlings before release, and the emergence (or re-emergence) of headstarting programs throughout countries in the Indian Ocean and South-East Asia region were expressed at the 2nd and 4th Meetings of the Northern Indian Ocean Marine Turtle Task Force (NIO-MTTF). As a response, a version of this document was developed to inform Signatory States to the Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and South-East Asia (IOSEA Marine Turtle MoU) and made available on its website (https://www.cms.int/iosea-turtles/en/page/capacity-building-resources), so that evidence-based decisions about sea turtle management and conservation can be made. This paper in IOTN is a modified version of the IOSEA document, and presents an overview of the practices and concerns about holding and headstarting programs with reference to relevant sea turtle hatchling biology. Where possible, examples are drawn from research and conservation conducted in Signatory States to the IOSEA Marine Turtle MOU.
DEFINITIONS OF HOLDING AND HEADSTARTING
This overview regards holding and headstarting of hatchlings as distinct practices. There is no single, generally accepted definition of either term, so each is distinguished from the other according to length of time and purpose of the practice. Holding and headstarting facilities are usually associated with a turtle hatchery, a protected place to which threatened eggs can be moved and safely incubated in conditions similar to that on the natural nesting beach (Phillott & Shanker, 2018).
Holding is the practice of keeping or retaining hatchlings after their emergence from the nest, for a period of time that may range from hours to days, or longer. The purpose of holding hatchlings is to release them at a convenient time for hatchery personnel and/or display and release of hatchlings for the benefit of the hatchery and observers. Hatchlings may be retained in conditions ranging from a dry bucket or damp sack to a bucket or tank of water, depending on the length of time for which they are held.
Headstarting is the practice of raising hatchlings in captivity to a larger size, before their release to the wild. Protecting hatchlings from predation is believed to increase the likelihood of their survival, a priority for conservation of the population or species (Mrosovsky, 1980).
(Note that holding and headstarting of hatchlings differ from each other. Holding and headstarting are also different to farming, ranching, and/or captive breeding sea turtles for commercial purposes, such as the harvest of meat, shell, leather and other commodities that derive from sea turtles (e.g., blood, oil, fat, bones), and/or conservation (Ross, 1999). This overview considers holding and headstarting only.)
Holding and headstarting are among the conservation/management actions that have described as “halfway technology” (Frazer, 1992). While usually practiced with good intentions, holding and headstarting alone do not directly address or reduce direct threats to sea turtle populations- including interactions with fisheries, illegal take, and loss of habitat- and can interfere with hatchling biology and behaviour, reducing their chances of survival.
SEA TURTLE HATCHLING BIOLOGY
Depending on species and incubation conditions in the nest, sea turtle embryos have a 6-13 week incubation period (Miller, 1996). Once hatchlings have escaped the eggshell, internalised (absorbed) any remaining egg yolk and straightened their body which is slightly curled after being inside the egg, hatchlings dig to the top of the nest in a cooperative manner with their siblings (Carr & Hirth, 1961) and wait below the surface of the sand. En masse hatchling emergence from the nest onto the beach is stimulated by a decrease in sand temperature and, therefore, usually occurs at night (Miller et al., 2003).
Survival of hatchlings depends greatly on their ability to emerge from the nest, run down the beach, swim out through nearshore waters, and reach offshore waters as quickly as possible. In the minutes spent crossing the beach, hatchlings use cues such as illumination and beach slope to orient towards the sea (Salmon et al., 1992). Crawling across the beach is believed to be crucial for hatchlings as it allows them to imprint on their natal beach and return to the area when they are ready to reproduce, known as nesting beach fidelity (see Lohmann et al., 2013).
Once in the water, hatchlings enter a period of hyperactivity (Carr, 1963), known as the swimming “frenzy”, during which they swim continuously for about 24hr. The swim frenzy allows them to minimise the time spent in coastal waters where predators are more abundant (Wyneken & Salmon, 1992; Gyuris, 1994; Wyneken et al., 2008). A combination of cues from wave direction and the light horizon helps hatchlings to orient offshore (Goff et al., 1998; Pilcher et al., 2000). After the initial frenzy, hatchlings use currents and periodic, active swimming to find suitable habitats (Salmon et al., 1992; Mansfield et al., 2014; Putman & Mansfield, 2015; Briscoe et al., 2016; Gaspar & Lalire, 2017; Gatto & Reina, 2020). Feeding does not start until they reach foraging habitat, about 1 week after emerging from the nest. Energy used for all hatchling activities, from when they hatch from the egg to when they first begin to feed, is derived from the residual yolk left from the time of hatching (Kraemer & Bennett, 1981).
Once out of the nest and on the beach, hatchlings face threats such as predators, physical obstacles, and light pollution, as well as high sand temperatures which can cause burns or over-heating and mortality if they emerge during the daytime. After entering the sea, hatchling numbers are reduced further by depredation. It is hard to study hatchling mortality at this time, but limited studies indicate that hatchling number can be reduced by an average of ~20% within the first 30min (Oñate-Casado et al., 2021) and 40-60% (and potentially up to 80%) within the first 2hr (Pilcher et al., 2000) of entering the sea. Hatchlings eaten by terrestrial and marine predators play an important role in coastal food chains and nutrient cycles (Bouchard & Bjorndal, 2000; Madden et al., 2008; Vander Zanden et al., 2012; Heithaus, 2013) so hatchling predation should only be controlled if it has the potential to reach unsustainable levels (Phillott, 2020).
BEST PRACTICES FOR RELEASING SEA TURTLE HATCHLINGS
Nest management before hatchling release
Nests in a hatchery should be individually enclosed with a basket or non-metallic cage (see Figure 1) before the predicted emergence date to prevent hatchlings from crawling throughout the hatchery and intermixing with hatchlings from different clutches. The predicted emergence date is usually about 45-55 days after oviposition. About 2-3 days before hatchling emergence from the nest, hatchling personnel may observe the sand surface immediately above the nest collapsing or caving inwards as the volume of the nest contents decrease due to hatchlings emerging from the eggs.
Individual nest enclosures should be checked every 30-60min from afternoon to dawn and at other times when hatchlings may emerge (e.g., on overcast days and/or after rain) during the predicted emergence dates. Individual nest enclosures should be removed when hatchery personnel are not available to monitor the nests, so that hatchlings do not become exhausted or overheated. The fence or enclosure surrounding the hatchery should protect eggs and hatchlings from threats such as depredation and illegal take, but also be designed to allow the exit of hatchlings from the hatchery if they emerge when personnel are not present (see Phillott & Shanker, 2018).
When to release hatchlings
The best practice for hatcheries is to release hatchlings as soon as possible after their emergence from the nest. This prevents hatchling exhaustion, dehydration, overheating, depletion of the energy reserves in the yolk which is needed for movement from the beach to offshore, injury, and even death. Hatchlings that emerge in the heat of day or at a time when immediate release is not possible can be housed in a soft, damp cloth or sack (made of tightly woven material so hatchling claws do not become entangled) in a cool, dark place until release (see Phillott & Shanker, 2018).
Where to release hatchlings
Hatchlings should be released in groups to improve the likelihood of survival. However, early emergers from a nest should not be held until more hatchlings emerge as this practice can result in loss of energy (through consumption of the stored yolk). Terrestrial and aquatic predators will congregate at locations which are regularly used for hatchling releases, so release sites should be random and hundreds of metres apart. Hatchlings should be released so they crawl across the beach and enter the ocean to allow imprinting on their natal beach, as this is believed to facilitate return of sea turtles to breed in the same region where they originally hatched (Phillott, 2020).
Providing for observers during hatchling release
To ensure hatchling safety while allowing observers the opportunity to watch hatchlings as they run to the sea, the following steps are recommended (adopted from Mortimer, 1999; Sea Turtles of India, 2011):
- Type of project (Non-Profit, Academic Institution, For-Profit, Government, or Other)
- Create a safe hatching release and crawling area by drawing parallel lines in the sand, about 10m apart and perpendicular to the ocean. Fill any holes and smooth the sand in the safe hatchling area between the hatchling release point and the sea, and remove marine debris and other obstacles.
- Ensure that observers remain outside the lines that mark the safe hatchling area so hatchlings are not accidentally trampled.
- Release hatchlings into the area between the lines to ensure their safety and allow observers to have an unobstructed view of the hatchlings as they crawl down to the sea.
- Place a dim torch or flashlight on the sand as close as possible to the sea, with the light directed landward during night-time releases. This light will help to guide hatchlings so they remain within the safe area and allow observers to see them at night. The torch/flashlight should be switched off when the majority of hatchlings enter the sea so they are not attracted back on to the beach.
- Do not permit camera flashes to be used while filming/photographing hatchlings during night-time releases as the artificial light will cause disorientation.
- Warn observers close to the water not to jump or step to avoid waves as they might step on hatchlings when they are close to or entering the sea.
- Hatchlings that are taking minutes longer than their siblings to cross the beach and enter the sea can be carried to the water and released once the majority of hatchlings have departed.
Figure 1: Woven basket (left), plastic mesh cages (centre), and wood and mesh cages (right) that enclose individual nests and prevent emerged hatchlings from crawling throughout the hatchery. (Photo credits: Andrea D. Phillott and Nupur Kale)
CONCERNS ABOUT HOLDING SEA TURTLE HATCHLINGS
Holding hatchlings for any time period will result in them unnecessarily using energy reserves that are needed to crawl across the beach and swim quickly through inshore waters to avoid predators and reach their first feeding habitat. Multiple studies have shown that hatchlings that are held before release will crawl and swim at slower speeds and swim with less powerful strokes (Table 1). Hatchlings that are slow and less powerful swimmers will take longer to reach offshore habitats, and will be at greater risk of predation. Hatchlings that do not reach their foraging grounds before their energy reserves are depleted are at greater risk of death (Mansfield et al., 2014).
Table 1. Research conducted in various Signatory States of the IOSEA MoU that assessed crawl and/or swim performance in hatchlings which are held before release.
For these reasons, hatchlings should be released as soon as possible after emergence from the nest and not held within the hatchery fence or nest enclosure, or in a bucket, sack, pond or tank etc., for reasons of convenience, scheduled public releases, or unjustified concerns about their health (see Phillott et al., 2018, 2021; see also Examples 1-3).
Example 1: Holding conditions put hatchlings at risk of injury and/or death
Some hatcheries bury a bucket to sand level (see red arrow) to collect hatchlings at night, attracting hatchlings using a torch inside the bucket. When nests are not enclosed or monitored overnight, the bucket saves the hatchery personnel time and effort in gathering all the hatchlings when they arrive in the morning. Hatchlings held in this way can be injured, crushed, and potentially die if many hatchlings emerge overnight and accumulate in the bucket.
This practice must not be used.
(Photo credit: Andrea D. Phillott)
Example 2: Holding conditions use hatchling’s energy reserves before release
Sundaram et al. (2019) described a hatchery practice of digging a bowl of seawater into the beach surface so that hatchlings emerging during the night, when nests are not monitored, would not get dehydrated. Holding hatchlings in conditions where they are crawling and/or swimming for extended periods depletes the valuable energy reserves needed to cross the beach and swim quickly through coastal waters to reach offshore feeding habitats and is not a best practice for hatcheries. Hatchlings do become dehydrated between hatching from the egg and emergence from the nest due to the energy required to escape the nest (Sundaram et al., 2019). However, exposure to humid air after emergence does not result in greater dehydration (Fujimoto et al., 2020). Further, hatchlings held in dry conditions have a stronger swim stroke than hatchlings held in seawater (Balsalobre & Bride, 2016), so providing hatchlings with water to swim in before release reduces their fitness.
Hatchery design should allow hatchlings that emerge at night to escape the hatchery without intervention if nests cannot be monitored.
Example 3: Holding hatchlings for unjustified health reasons
Hatcheries that hold hatchlings for several days have justified this practice as protecting hatchlings against attack from marine leeches (Hewavisenthi & Kotagama, 1990) or predatory fish (see Richardson, 1996) at the site where the yolk is absorbed. However, there is no evidence that leeches or fish attack hatchlings at this site. This unjustified concern is perceived as an excuse for holding hatchlings that will attract tourists to hatcheries that are also operating as business ventures (Richardson, 1996).
This practice should be discontinued immediately (Phillott et al., 2018).
RECOMMENDATIONS FOR HOLDING HATCHLINGS
The majority of hatchlings should not be held before release unless they emerge in bright daylight hours. Hatchlings crossing the beach in the daytime will experience more predation (Pilcher & Enderby, 2001), and be at risk of overheating, dehydration, and death. If a public hatchling release is assessed as having high promotional, educational, or economic value for important or special guests, students, and tourists, then <10% of hatchlings from a clutch, and including hatchlings that remain in the nest after the majority of the clutch emerges, can be held for this purpose. The hatchling release should occur in the early morning (before ~7am) or late afternoon (after ~5pm). Observers of the hatchling release should be made aware of why there are limited numbers of hatchlings to observe and understand that holding healthy hatchlings for scheduled release reduces their chance of survival.
If hatcheries do not have enough personnel, including volunteers, to monitor nests around the predicted emergence date and immediately release hatchlings, then hatchlings should not be retained until it is convenient to release them. Instead, nest enclosures should be removed when personnel are not present and the hatchery fence material should allow hatchlings to escape the hatchery and crawl to the sea without human assistance (see Phillott & Shanker, 2018). Obstacles between a hatchery and the ocean and light sources around and inland of a hatchery should be minimised, so hatchlings are not disoriented away from the sea, and do not unnecessarily exert additional energy trying to escape or avoid obstacles or and reorient trying to find the most direct route to the sea.
CONCERNS ABOUT HEADSTARTING SEA TURTLE HATCHLINGS
Early concerns about headstarting included questions about whether sea turtles could imprint on their natal beach, survive in the wild, complete a successful breeding migration, be tagged for later identification, what proportion of eggs should be incubated in headstarting programs, how the success of such programs could be assessed, and if protection if other life stages would be a better option than headstarting (Pritchard, 1979; Mrosovsky, 1980; Pritchard, 1980; Allen, 1981; Buitrago, 1981; Goodwin, 1981; Pritchard, 1981). Some of these questions have been answered by long-term studies of a number of projects, including the Cayman Turtle Farm (see Example 4), and the Kemp’s Ridley Sea Turtle Restoration and Enhancement Program (see Example 5).
Example 4: Cayman Island Turtle Farm
Sea turtle nesting populations at Grand Cayman Island were decimated by a fishery operating from mid-1600’s to late-1700’s, and less intensively after that time. Local nesting populations were believed to have become extinct and foraging populations to be very small in the 1900’s (see Aiken et al., 2001; Barbanti et al. 2019). In 1968, the Cayman Turtle Farm was established to restore local green turtle populations and provide an alternative source of turtle meat to reduce harvest of wild turtles. Adult turtles and/or eggs were imported from Ascension Island, Costa Rica, Guyana, Mexico, Nicaragua, and Suriname to establish a captive breeding population at the farm. Offspring of different captive bred generations were raised for 4–6 years and then released into the wild, kept as breeding stock, or slaughtered for meat production (see Barbanti et al., 2019). Wild nesting populations have increased in the Cayman Islands, with about 430 green turtle nests, about 240 loggerhead turtle nests, and 4 hawksbill turtle nests recorded in 2019 (see Blumenthal et al., 2021). Recovery of the green and loggerhead (but not hawksbill) turtle nesting populations is due to a combination of various conservation actions, including release of about 16,500 captive bred hatchling and about 14,500 yearling green turtles from the Cayman Turtle Farm between 1980 and 2001 (Bell et al., 2005), protection of in situ nests (see Blumenthal et al., 2021), legislation that prohibits possession of eggs and interference with nesting turtles (Bell et al., 2006), changes to turtle fishery regulations to stop the take of adult turtles and extend seasonal closures (Blumenthal et al. 2010), and the end of legal take of sea turtles in 2008 (Nuno et al., 2018). Criticisms of the Turtle Farm included stress, injury, and disease due to sea turtles being kept in captivity (Arena et al., 2014), and international trade infractions (Donnelly, 1992).
Example 5: The Kemp’s Ridley Sea Turtle Restoration and Enhancement Program
The nesting population of Kemp’s ridley turtles at Rancho Nuevo, Mexico, declined from an estimated 40,000-42,000 nesters in a single “arribada” (mass nesting event) to about 700 nests in a season from 1947 to 1985 due to fisheries bycatch and illegal take of eggs. The Mexican Government started protection of eggs and females at Rancho Nuevo in 1966, and efforts to establish a secondary nesting colony at South Padre Island in Texas commenced in 1977, as a safeguard against the species’ extinction. The island is within the historical nesting range of the species. Eggs were transferred from Rancho Nuevo to South Padre Island and exposed to sand from the island to imprint embryos/hatchlings to this location. Hatchlings from Padre Island, Rancho Nuevo and Cayman Turtle Farm, were also exposed to the sea at Padre Island to facilitate imprinting and then headstarted in a lab for 7-15 months before release with a tag to allow them to be later identified. Close to 13,500 headstarted hatchlings imprinted to South Padre Island were released from 1978-2000. The first imprinted, headstarted turtle was found nesting at Padre Island in 1996. A peak of 210 Kemp’s ridley nests were recorded on the south Texas coast in 2012. The age, size, feeding, behaviour and reproductive biology of headstarted turtles is similar to that of wild Kemp’s ridleys (see Manzella et al., 1988; Shaver, 1991; Taubes, 1992; Zug et al., 1997; Shaver & Wibbels, 2007). Protection of turtles and eggs at the nesting beach and the introduction of compulsory turtle excluder devices (TEDs) on US trawlers are likely to have contributed to increasing numbers (see Lamont et al., 2021).
Both projects show indications of success: captive-bred green turtles from the Cayman Turtle Farm are nesting in the Cayman Islands, and imprinted, headstarted Kemp’s ridley turtles are nesting on the Texas coast (see Shaver & Caillouet Jr., 2015). Headstarting has contributed greatly to the recovery of green turtle populations in the Cayman Islands (Barbanti et al., 2019); other conservation actions, including protection of in situ nests (see Blumenthal et al., 2021), legislation against possession of eggs and interference with nesting turtles (see Bell et al., 2006), changes to turtle fishery regulations (see Blumenthal et al., 2010), and the end of legal take of sea turtles (Nuno et al., 2018), also contributed to increasing green (and loggerhead, but not hawksbill) turtle populations in the area. Similarly, the protection of in situ nests and nesting turtles, reduction in US trawlers and seasonal closures in Mexico waters, and requirement for US trawlers to use turtle excluder devices (TEDs) assisted with increased numbers of Kemps ridley turtles (see Caillouet Jr., 2019). It should be noted that the number of nesting Kemp’s ridley turtles to date represents only a small fraction of the total number of headstarted hatchlings, and early estimates of survivorship to maturity was estimated to be ten times higher in wild Kemp’s ridleys at Nuevo Rancho than for headstarted turtles from Padre Island (Heppell & Crowder, 1998). A longer study is needed to estimate if this trend in Kemp’s ridley continues or improves, and forthcoming publications should compare the survivorship between wild and headstarted turtles in the Cayman Islands.
A major concern of the Kemp’s Ridley Sea Turtle Restoration and Enhancement Program was the unintentional production of predominantly male hatchlings in the early years of artificial incubation of eggs, before it was known that incubation temperature determined the sex of the hatchlings. This was corrected later in the project by the deliberate manipulation of incubation temperature to produce predominantly females (see Bowen et al., 1994). The risk of interfering with as-yet unknown, or incompletely understood, aspects of sea turtle biology are still a risk for current and future headstarting projects. For example, the large number of small sea turtles entering the population from the Kemp’s Ridley Sea Turtle Restoration and Enhancement Program, without the natural predation of eggs and hatchlings, may actually be limiting population recovery through competition for food and other resources (Caillouet Jr., 2019), and a reduction in production of hatchlings may be required (Caillouet Jr., 2021). Headstarting also carries risks of stress, injury, disease and parasite outbreak (Arena et al., 2014; Crespo-Picazo et al., 2017; Orós et al., 2020), and turtles could need exercise (Stabenau et al., 1992) and to be familiarised with wild conditions and habitats to increase chances of survival (Okuyama et al., 2010). The location and season (influencing water temperature) at which headstarted turtles are released can also be important for offshore migration (Mansfield et al., 2009).
RECOMMENDATIONS FOR HEADSTARTING HATCHLINGS
The Cayman Island Turtle Farm and the Kemp’s Ridley Sea Turtle Restoration and Enhancement Program were responses to populations in crises due to overexploitation of turtles and eggs and/or high bycatch rates and mortality in fisheries. Population models show that protecting sea turtles in the first year of their life is unlikely to be effective unless sub-adult and adult survival is also maximised, and conservation efforts should protect older life stages through reducing fisheries bycatch rather than just hatchlings through headstarting (Heppell et al., 1996, 1999).
Facilities that house and display sea turtles can present opportunities for education and raising awareness among students of different ages, other community members, government officials, tourists, as well as a source of community livelihoods. However, vigorous hatchlings which emerge from the nest without assistance should not be headstarted for this purpose. Instead, hatchlings which remain in the nest after the majority (about 80%) have emerged, and turtles that require treatment or rehabilitation such as those that have stranded or been recovered from fishing gear, including ghost gear, can be used for display and potential release. Personnel at such facilities should consult up to date research and guidelines to be informed about the best understanding of suitable conditions for sea turtle housing, feeding, health monitoring etc (Okuyama et al., 2010; Kanghae et al., 2016, 2017; March et al., 2019; Jualong et al., 2021). Educational materials at the facility can educate visitors about the natural biology of sea turtles, threats to local and global populations, local conservation efforts (and why holding and headstarting healthy hatchlings are not one of them), and actions that visitors to the facility can take to help conserve sea turtles.
CONCLUSION
Sea turtle eggs, hatchlings and post-hatchlings are vulnerable life stages, but they also have important roles in coastal ecosystems, where, among other things, they serve as a valuable nutrient source (reviewed by Patel et al., 2022). Holding or headstarting hatchlings removes them from their natural role as prey for terrestrial and marine predators, interrupts their biology, may have limited benefits at the population level, and can reduce the health, fitness, and survivorship of individuals. Holding and headstarting also fail to address the cause of declines in sea turtle populations. Vulnerable sea turtle populations in the IOSEA region would benefit the most from reduced anthropogenic threats, including mortality after interaction with fisheries (Heppell et al., 1999) and illegal take for trade (IOSEA, 2014; CMS & IOSEA, 2022).
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