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Direct observation using human swimmers has proved to be an acceptable experimental protocol to follow in order to study neonate swimming and diving behavior. This study documents the observations made on hawksbill, Eretmochelys imbricata, neonates on their first day after hatching from the coral reef archipelago at Cayos Cochinos Biological Reserve, Honduras. The Cayos Cochinos Biological Reserve (CCBR) is located on the northern Honduran shelf, western Caribbean (Fig. 1).

Hawksbill neonates in this study hatched from three clutches located on different beaches (Playa Dos, Paloma and Cordero) and nights from CCBR during the nesting season from June through October of 1998. Eggs were collected from the nests as they were laid and incubated at the CCBR hatchery on Cayo Menor. Immediately after hatching usually just prior or immediately after sunrise, all neonates were placed in plastic trays with some sand and kept in the dark at room temperature for approximately three hours prior to release, which took place within one hour after sunrise at their respective beaches of origin. Once all neonates from the clutch were released on an area of the beach where hawksbill eggs are normally laid (1-5 m above the highest tide at the study site), the time and geographic reference point was recorded using a hand-held global positioning system (GPS; Magellan). Simultaneously, four neonates were chosen at random and individually followed from the surf into the ocean by observers equipped with mask, snorkel and fins. The four observers followed their corresponding neonates keeping a distance of approximately 1.5m behind the hatchling. A boat man followed at a minimal distance of 100 m from the observers in a 12 foot outboard motorboat. To avoid exhaustion, an alternate person replaced each observer every two to three hours. To allow the boat man to keep sight of each observer, each swimmer trailed from his or her waist a 6m line with a buoy and life vest at its end. The boat man recorded the GPS position from each observer every hour by turning off the motor and paddling close to the observer (< 25 m). Observations on the approximate diving depths and surfacing intervals of each neonate were recorded using stop-watches. Neonates were followed throughout the day, discontinuing observations approximately one hour before dusk to avoid navigating towards the station at night. Surface water current direction was determined by using a compass; its strength was not quantified. To observe feeding behavior in captivity, thirty sibling neonates of the study group were held in the CCBR in a three m-circumference tank with a Sargassum float in it collected the day the neonates were placed in the tank.

Twelve neonates were followed on separate days during August 1998: four from Playa Dos, four from Paloma and four from Cordero (Fig. 2). All neonates, independent of their release site, initially swam vigorously once entering the surf, remaining close to the surface except for sporadic dives between 1-4 m. The observers lost three neonates as they dove below ~ 4 m depth. It was not possible to determine what influenced neonates to dive deep and no predators were apparently present to frighten them. These dives appeared to represent normal, but infrequent aspect of behavior.

During the first hour of observations, diving and surface times were recorded. Neonates from all clutches remained swimming just below the water surface (5-10 cm) for 10 to 56 sec before taking a breath (mean ± sd = 23 ± 2.5 sec, n = 134 total observations from 12 neonates). Sporadically neonates swam deeper (but usually within 1m), with dives lasting for 12-35 sec (mean = 15 ± 1.9 sec, n = 130 observations). When fish swam close to them, the neonates assumed an immobile position by folding both front flippers along the top of its carapace and joining its back flippers medially as reported by Witherington and Salmon (1992) for Caretta caretta. Neonates would then remain motionless for minutes (< 5) before resuming swimming. This same pattern of behavior was observed after one individual was bitten and released by a flat needlefish, Ablennes hians.

Figure 1. Location of the Cayos Cochinos Biological Reserve study site. Arrows indicate the prevailing superficial ocean current patterns. Notice the counterclockwise gyre at the study site (taken from Brenes et al. 1998).

The first group of neonates, released at Playa Dos, was confronted with a northeast to southwest surface current (Fig. 2). Turtles from this group swam against the current throughout the observation period (7 hrs) with a mean (± sd) within group speed of 0.7 km.hr^-1 ± 1.03, n = 20 observations). The final observation was recorded 4.6 km from shore.

Turtles of the second group released at Paloma were confronted with a northwest to southeast current (Fig. 2). They all swam against the incoming surface current for the first hour, but then started to drift in a southeastern direction with the current. Two neonates individually encountered small (ca.1 m²) floats of Sargassum seaweed at 2.4 km and 2.8 km, respectively, away from their release site. Once in the seaweed float, they became motionless and drifted passively for the following 2 hrs until observation was discontinued. Turtles from this group which where not associated with Sargassum swam/drifted at an average speed (±sd) of 1 km.hr^-1 ±0.67, n= 13 observations. A slightly slower speed was recorded by those neonates once they became associated with the drifting Sargassum (average of two neonates: 0.9 km.hr^-1 ±0.91, n=11) but this difference was not significant (Student t test; P 0.05).

The most conspicuous dwelling faunal species from observed Sargassum floats in this study were shrimp, crabs, fish (Balistes sp.), nudibranchs and snails. As suggested by Carr and Meylan (1980), neonates remaining in Sargassum floats most likely feed on the dwelling organisms in this microecosystem. Sibling neonates of this second group held at the CCBR tank with a Sargassum float in it fed after four days of hatching on both the Sargassum and on its dwelling fauna.

The third group of neonates, released at Cordero, was confronted with a west to east current (Fig. 2).

Figure 2. Course taken by neonates released on 3 beaches from the Cayos Cochinos Biological Reserve: 1) Playa Dos, 2) Paloma and 3) Cordero, during different days. The filled arrows depict superficial current directions at the corresponding days of release. The thin arrows represent the overall off-shore direction of dispersal of the observed neonates.

Similar to the first and second group, individuals swam against the incoming current but were almost immediately carried by the current in an easterly direction into deep (>10 m) waters. The current swept the observed individuals into a shallow area between two coral cays (Balfate and Cayo Largo Arriba). Once in the shallow waters (1-2 m), neonates stopped swimming, resuming their swimming only after they were again in deeper (> 6 m) waters. It is presumed that this was to avoid predation by coral reef dwelling fish. Turtles from this group were an average 2.3km away from their release point when the study was discontinued, and had swum/drifted at an average speed (±sd) of 0.7km.hr^-1 ± 0.95, n= 14 observations, similar to the first group of observed neonates which apparently did not drift.

Neonates swam against the incoming waves upon entering the sea, but soon swam and drifted in an eastern and-northeastern direction into the open ocean, independent of varying depths and surface current direction. It is difficult to determine where these neonates might have eventually swam/drifted to, however the surface water of the northern shelf of Honduras is affected by a small counter-clockwise current whose flow directly washes the offshore Honduran Bay Islands including the archipelago at CCBR (Fig. 1; US-Defense Mapping Agency 1990). The direction where neonates headed seems congruent with this current which could maintain them close to the reef system from the Honduran shelf. It has been suggested that some hatchlings/juveniles might remain on reefs close to their natal beaches (Witzell & Banner 1980) although there is little evidence to support this. Additionally, Davenport and Clough (1986) proposed that more coastal and less migratory species (such as hawksbills) might be expected to spend more time swimming slowly. Findings presented here may be supportive of these theories as most observed neonates appear to have swum very little and rather they drifted becoming associated with Sargassum. However with these observations it is impossible to determine if these neonates remained within the small counter-clockwise current (Fig. 1) or eventually dispersed into the surface water current of the Caribbean which flows into the Caribbean Sea through the Lesser Antilles and also through the Greater Antilles (Fig 1; Stalcup & Metcalf 1972).

The observations of neonates interrupting their swimming activity during their first day dispersal when encountering and remaining in Sargassum floats is interesting and may also indicate that hawksbill neonates from this study site could remain closely associated with the reef system off Honduras as opposed to dispersing far away from their natal beaches and into the wider Caribbean. This however, may be assessed with the use of molecular markers and a more finely tuned analysis of the surface water currents. The observed association between neonates and Sargassum floats also concurs with previous observations that juvenile sea turtles use these floats as habitat (Carr 1986; Carr & Meylan 1980) and is consistent with sporadic reports from local fishermen of neonates entangled in Sargassum when the latter are washed ashore after heavy storms.

Acknowledgements: Gratitude is expressed to the Coral Reef Fund, Universidad Autónoma de Honduras and Universidad Católica and to C. García-Saez, A. Cubas, E. Aguilar, A. Paredes. The manuscript was improved by the comments of two reviewers.

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