AMER. ZOOL., 20:525-530 (1980)
The "Lost Year" Question in Young Sea Turtles1
ROSS WlTHAM
Florida Department of Natural Resources Marine Research Laboratory,
100 Eighth Avenue SE, St. Petersburg, Florida 33101
SYNOPSIS. An adequate understanding of young sea turtle dispersal patterns is necessary
for effective management of threatened or endangered species. Such patterns are poorly
understood, and the term "lost year" has been adopted to emphasize this gap in sea turtle
life history information. Tag returns from pen-reared yearling sea turtles indicate ocean
current dispersal. Evidence indicates hatchlings would be similarly dispersed by ocean
currents. Feeding studies with tank-held animals suggest that food resources are available
in ocean currents for long-term sea turtle survival. Green turtle (Chelonia mydas) growth
appears slow in nature.
INTRODUCTION
681). After reaching a weight between 200
The posthatchling period, or "lost year" and 900 g, turtles are released on beaches
of sea turtle life history, after departure during daylight. Observations are made
from natal beaches, is poorly understood. during turtle movement to the sea and for
The turtles' coloration, small size, and agil- as long as possible after they start their offity make oceanic observations difficult. shore swim.
Data acquisition during this extended
RESULTS
posthatchling period is further impeded
Tag returns from pen-reared, yearling
by lack of suitable, durable tags for hatchlings. However, in our continuing Jensen green turtle releases made in the 1960s inBeach study, tag returns from yearling dicated some long-term survival and
green (Chelonia mydas Linne) and logger- movement (Witham and Carr, 1968; Carr
head (Caretta caretta Linne) turtles are pro- and Sweat, 1969). More than 10,000 turviding data on oceanic survival, growth, tles have been released since large-scale
efforts were begun in 1972; more than 90
and dispersal.
tag returns have been received. Although
some returns have been short-term recapMATERIALS AND METHODS
Turtle eggs are collected from natural tures near release beaches, most have been
nests on Florida's east coast, then incubat- long-term, long-distance returns (Table 1,
ed and hatched in the laboratory. Hatch- Fig. 1). These data indicate slow oceanic
lings are reared in facilities previously de- growth (Fig. 2).
scribed by Witham (1976) and Witham and
DISCUSSION
Futch (1977). Additional facilities are also
Numerous
authors
have suggested that
provided at Sea World, Orlando (closed,
artificial sea water system) and at a private ocean currents influence sea turtle disestate at Hillsboro Beach (open sea water persal. Deraniyagala (1939), in his zoogeographic discussion of testudinates, mensystem).
Prior to release, all turtles are weighed tioned the seasonal clockwise and
and measured, then tagged with self pierc- counterclockwise currents around Ceylon
ing monel tags (National Band and Tag (Sri Lanka). Daniel and Smith (1947) comCompany,2 Style No. 4-1005, Size No. mented that for hatchling loggerheads,
". . . the current sense . . . and direction of
movement . . . may be influenced by the
1
From the Symposium on Behavioral and Reproduc- water currents of the surf, water pressure
tive Biology of Sea Turtles presented at the Annual factors, or other physical circumstances
Meeting of the American Society of Zoologists, 27- . . . ." Carr and Ogren (1960) mentioned,
30 December 1979, at Tampa, Florida.
"current sense" and "passive drifting" for
2
Use of product name does not indicate endorse- Caribbean green turtles. Little is known
ment by the Florida Department of Natural Reabout the local currents which might affect
sources Marine Research Laboratory.
525
526
ROSS WlTHAM
AZORES
VIRGINIA;CT|
N. CAROLINA"
S. CAROLINA
ATLANTIC
OCEAN
FIG. 1. Capture locations of pen-reared green turtles, Chelonia mydas, released by the Florida Department
of Natural Resources. Numbers refer to the number of turtles captured in each area.
the Tortuguero nesting colony (Carr et ai,
1978). Hughes (1974), Hughes and Richard (1974), Balazs (1976), and Pritchard
(1976) all discussed ocean current transport. Witham (1976) argued strongly for
ocean current transport of young sea turtles and suggested that such currents
might also be important to adult sea turtle
dispersal.
Observations of thousands of yearling
sea turtles, released on beaches and allowed to crawl to the sea, indicate that turtles orient themselves toward light until
they reach the surf (Daniel and Smith,
1947; Ehrenfeld, 1968; Mrosovsky, 1972).
Upon reaching surf with sufficient wave
action, turtles unhesitatingly swim seaward. When waves are very small or absent, the turtles hesitate, and swimming
appears non-directed. A wave orientation
response has also been observed by students from the Florida Institute of Technology (FIT) (personal communication).
Frick (1976) reported that hatchling
green turtles swam at an average 1.57 km/
hr when moving offshore. Prang (1976),
while studying swimming turtle energetics,
X"
"
x*x
12 14 16 18
WEIGHT (Kg)
20 22
24
a6
28 30
FIG. 2. Wild growth (weight) of 31 pen-reared green
turtle yearlings released by the Florida Department
of Natural Resources.
527
YOUNG SEA TURTLE SURVIVAL, GROWTH, DISPERSAL
TABLE 1. Released and captured data for pen-reared, yearling turtles tagged and released on Florida beaches.*
Released
Tag no
A451
A498
A681
A1037
A1195
A1216
A1319
A1395
A1573
A1631
A1672
A1698
A1993
A1999
A2155
A2250
A2316
A2480
A2575
A3147
A3291
A3554
A3566
A3626
A3643
A3667
A3756
A3770
A3798
A3903
A3903
A3903
A3909
A3915
A3939
A4045
A4049
A4125
A4125
A4160
A4591
A4621
A4681
A4958
A5053
A5485
A5664
A5719
A5856
A5973
A6083
A6097
A6110
A6146
A6232
A6281
A6316
A6340
A7020
Date
31 May 72
9Jun72
4 Apr 72
19Sep72
24 Apr 73
25 Apr 73
16 May 73
16 May 73
17 May 73
23 May 73
6Jun73
6Jun73
18 Mar 74
18 Mar 74
27 Mar 74
27 Mar 74
27 Mar 74
17 Apr 74
29 May 74
13 Mar 75
21 Mar 75
2 Apr 75
2 Apr 75
16 Apr 75
16 Apr 75
16 Apr 75
16 Apr 75
16 Apr 75
16 Apr 75
25 Apr 75
9 Feb 76
23 May 76
25 Apr 75
25 Apr 75
25 Apr 75
2 May 75
2 May 75
2 May 75
7 Oct 77
2 May 75
10Jun75
29 Jul 75
29Jul75
21 Jan 76
21 Jan 76
26 Mar 76
31 Mar 76
31 Mar 76
14 Apr 76
14 Apr 76
3Jun76
3Jun76
3Jun76
3Jun76
25Jul76
25 Jul 76
25 Jul 76
25 Jul 76
7 Apr 77
Capture
N Lat
W. Long.
27°15'
27°15'
26°30'
25°40'
27°10'
27°10'
25°40'
25°40'
26°30'
27°15'
28°30'
28°30'
26°30'
26°30'
25°40'
25°40'
25°40'
27°50'
28°30'
27°15'
26°30'
27°15'
27°15'
25°40'
25°40'
25°40'
25°40'
25"40'
25°40'
26°05'
17°30'
17°30'
26°05'
26°05'
26°05'
27°50'
27°50'
27°50'
34°45'
27°50'
27°15'
27°05'
27°05'
25°40'
25°40'
26°30'
27°15'
27°15'
27°15'
27°15'
27°05'
27°05'
27°05'
27°05'
27°15'
27°15'
27°15'
27°15'
25°40'
80° 10'
80° 10'
80°05'
80° 10'
80° 10'
80°10'
80°10'
80°10'
80°05'
80° 10'
80°35'
80 o 35'
80°05'
80°05'
80°10'
80°10'
80°10'
80°25'
80-35'
80°10'
80°05'
80°10'
80° 10'
80°10'
80°10'
80°10'
80-10'
80°10'
80°10'
80-05'
88°10'
88°10'
80°05'
80°05'
80°05'
80°25'
80°25'
80°25'
76°25'
80-25'
80°10'
80°10'
80-10'
80°10'
80°10'
80-05'
80°10'
80°10'
80°10'
80°10'
80°10'
80°10'
80-10'
80-10'
80°10'
80°10'
80°10'
80°10'
80-10'
Date
Sep 76
May 79
25 Sep 78
26 Oct 72
7 Feb 76
15 Apr 76
19Nov75
25 May 73
23 Mar 78
24 Jan 77
23 Jul 77
30 Oct 76
23 Jan 78
20 May 76
20 Jan 77
10 Jan 75
28 Mar 74
15 Jan 77
15 Feb 78
28 Aug77
27 Apr 76
2 Apr 77
11 Nov 76
5 May 75
19 Dec 75
22 Apr 75
7 May 75
20 Jan 76
10 Oct 76
9 Feb 76
23 May 76
15 Jul 76
22 Nov 76
27 Dec 76
28 Jan 77
3Jun77
15 Sep 76
7 Oct 77
28 Nov 77
24Jul77
20 Jan 77
9 Nov 77
7Jun77
8 Feb 76
26 Jan 76
6Jun79
28 Dec 77
11 Oct 77
8 Dec 78
5 Apr 79
12Jul78
12 May 77
24 Feb 78
15 May 79
Aug 78
6 Feb 77
10 Nov 77
26 Aug 78
11 May 77
N Lat.
W. Long.
32°40'
32°45'
34°45'
25°10'
26°35'
22°50'
25-10'
25°40'
21°40'
28°45'
25-35'
26°35'
27°35'
32°40'
28-40'
10-30'
25-40'
18°15'
26°30'
33-50'
16°00'
27°40'
35°10'
25-40'
22°50'
25-40'
26°25'
25°05'
35°40'
17-30'
17-30'
17°30'
21°40'
17°30'
24°55'
17°05'
37-00'
34°45'
29°55'
27°20'
27O55'
33°50'
29°55'
27-15'
25°10'
26°30'
28°40'
35°05'
26°30'
27°40'
27°45'
19-35'
18-10'
13-10'
24°50'
39°25'
25°00'
19°35'
26-35'
79°50'
16-45'
76-25'
80°30'
77-50'
74°25'
80°30'
80°10'
71°45'
80°55'
76°40'
77°50'
80°35'
79°50'
80°45'
75-40'
80°10'
87°55'
77°05'
78°10'
86°00'
80°20'
75°45'
80-10'
74°25'
80-10'
80-05'
80°25'
75°10'
88°10'
88-10'
88°10'
71°20'
88°10'
80°40'
62°35'
76-05'
76°25'
81°20'
80°25'
82°50'
78°00'
81-20'
80°10'
80°25'
78°35'
80°45'
75°55'
78°35'
80°20'
80°25'
69°00'
87°55'
59°30'
76°20'
31-05'
77°55'
69°00'
80-05'
Location
S. Carolina
Ilha da Madeira
N. Carolina
Turkey Pt.
Bahamas
Bahamas
S. Biscayne Bay
Virginia Key
Middle Caicos
Titusville area
Bahamas
Bahamas
Vero Beach
S. Carolina
Mosquito Lagoon
Colombia, S.A.
Miami Beach
Mexico
Bahamas
N. Carolina
Honduras
Vero Beach
N. Carolina
Miami Beach
Bahamas
Miami Beach
Boca Raton
Key Largo
N. Carolina
Belize, C.A.
Belize, C.A.
Belize, C.A.
Turks-Caicos
Belize, C.A.
Long Key
Nevis, W.I.
Virginia
N. Carolina
St. Augustine
Satellite Beach
Clearwater
N. Carolina
St. Augustine
Hutchinson Isl.
Key Largo
Bahamas
Mosquito Lagoon
N. Carolina
Bahamas
Vero Beach
Sebastian
Dominican Rep.
Mexico
Barbados
Bahamas
Azores
Bahamas
Dominican Rep.
Lake Worth Beach
ROSS WlTHAM
528
TABLE 1. Continued.
Released
Tag no
A7027
A7045
A7054
A7157
A7182
A7206
A7257
A7485
A9062
A9222
A9249
Date
7 Apr 77
7 Apr'77
7 Apr '77
7 Apr 77
19 Apr 77
16 Apr 77
18 Apr 77
19 May 77
29 Aug 78
6 Feb 79
6 Feb 79
N. Lat
25°40'
25°40'
25°40'
25°40'
26°30'
26°05'
26°30'
26°50'
27°15'
27°15'
27°15'
iCapture
W. Long
80° 10'
80° 10'
80" 10'
80° 10'
80°05'
80°05'
80°05'
80°05'
80° 10'
80° 10'
80° 10'
Date
21 Apr 77
25 Apr 77
12Jun'77
13 May 77
19 Apr 77
28 Mar 79
13 Jan 79
23 May 77
1 Sep 78
19 Mar 79
25 Feb 79
N. Lat.
W. Long.
Location
25°30'
25°40'
25° 10'
26°50'
26°30'
17°2O'
35°10'
27°15'
27°15'
28°25'
26°30'
80°20'
80° 10'
80°25'
80°05'
80°05'
62°45'
75°45'
80°10'
80° 10'
80°30'
80°05'
Biscayne Bay
Bal Harbor
Key Largo
Juno Beach
Delray Beach
St. Kitts, W.I.
N. Carolina
Port Salerno
St. Lucie Inlet
Coca Beach
Delray Beach
* No. A498 was loggerhead, Caretta caretta. The others were greens, Chelonia mydas. Witham and Futch
(1977) reported 22 such returns for greens and their data are not repeated here.
found yearling green turtles did not swim
when currents were 0.14 m/sec (0.50 km/
hr) or less, and they became exhausted at
current speeds of 0.35 m/sec (1.26 km/hr).
An FIT report (unpublished) gave an average of 0.5 m/sec (1.8 km/hr) for yearling
green turtles swimming through surf.
Frick (1976), based on her observations of
the "swim frenzy" of hatchlings, suggested
they may swim steadily for 24 hr. This
might result in hatchlings being further
offshore than yearlings would be after 24
hr.
Hughes (1974) estimated that hatchling
sea turtles, entering the sea at a Caribbean
site, would require 4 to 7 yr to circumnavigate the North Atlantic and return to
their natal beach. Our data (Witham,
1976; Witham and Futch, 1977) indicate
that such a circumnavigation could take
less than 1 year in the North Atlantic gyre,
which includes the Florida Current and
Gulf Stream. The Florida Current, a
northerly flowing current near the Florida
east coast, reaches its maximum speed of
about 20 km offshore of Dade County
(Brooks and Niiler, 1977). The research
submersible, Ben Franklin, drifted more
than 2,596 km in 30 days while submerged
in the Florida Current and Gulf Stream
(Gatskell, 1973). The swimming behavior
of young sea turtles makes them comparable to vessels. Therefore the long-range,
rapid dispersal of hatchling turtles would
occur when they entered these major currents; off some Florida east coast beaches,
turtles would enter the current almost immediately. For example, hatchling turtles
swimming from a Dade County beach
would be deflected northward by the nearshore Florida Current (Dunlap and Shufeldt, 1969), and after 24 hr the turtles
would probably be about 130 km north of
the starting point (Fig. 3). Their longrange, rapid dispersal would continue until they left the major current. Dispersal
patterns for other beaches would be influenced by local currents and the Dade
County model should be modified to meet
local conditions.
It has been assumed that wild yearling
green turtles weigh from 1 to 4 kg (Hirth,
1971), but no data from wild populations
are available to support this assumption.
Caldwell (1962) suggested that green turtles would require 8 (tropical waters) to 13
yr (temperate waters) to reach maturity.
Our data (Fig. 2) indicate that pen-reared,
yearling green turtles grow slowly after
their release. These data suggest that 15 to
20 yr might be required for Western Atlantic green turtles to reach maturity. Balazs (1979) and Limpus (1979) estimated
that Hawaiian and Australian green turtles
might require as long as 50 yr to reach
maturity.
Captive feeding studies (Witham, 1977;
Witham and Futch, 1977) have shown that
green (Chelonia mydas), loggerhead (Caretta
caretta), and leatherback (Dermochelys coriacea Linne) turtles grow well on a diet of
one species of jellyfish, Cassiopea xama-
YOUNG SEA TURTLE SURVIVAL, GROWTH, DISPERSAL
110-
E
CO
o
POSITION OF TURTLE AFTER EACH
HOUR - ASSUMING NO CURRENT
40ESTIMATED POSITION OF TURTLE
AFTER EACH HOUR
529
Chesnut (1974) reported on the ctenophores, jellyfish, and Portuguese man-ofwar in coastal and neritic waters of North
Carolina. One widely distributed species of
jellyfish, Cyanea capillata, reaches a bell diameter of 2 m with tentacles 36 m long
(Halstead and Courville, 1965); one such
jellyfish might supply food for many small
turtles. Hirth (1971) reported that at an
indeterminate age green turtles become
primarily herbivorous, but adults continue
to eat jellyfish. The diverse fauna associated with drifting sargassum (Weis, 1968;
Fine, 1970; Ryland, 1974) might also provide supplemental food for turtles at sea.
Young sea turtles would probably find adequate food resources for survival in ocean
currents.
Our data strongly suggest that the initial
posthatchling period, "the lost year," is a
period of oceanic existence, when turtles
opportunistically use oceanic currents and
food resources for dispersal and survival.
ACKNOWLEDGMENTS
10-
Mt,
50
60
OFFSHORE DISTANCE (Km)
70
Fic. 3. Hypothetical positions of a hatchling green
turtle during 24 hours of easterly swimming from a
Dade County, Florida, beach.
chana Linne. The widespread oceanic distribution of cnidarians has been reported.
Mayer (1910) commented,
. . . I have frequently observed that they
[cnidarians] are more abundant near the surface when the ocean has been perfectly calm for
a few days than under ordinary conditions; for
if they are undisturbed by the movement of
waves, some of these forms, in common with
many of the rarely seen ctenophorae and siphonophorae, will gradually rise until they become in great numbers over the unrippled surface.
Piccard (1971), reporting on the drift
cruise of the research submersible, Ben
Franklin, observed salpas and jellyfish
throughout the trip. Kennedy (1972) discussed the widespread surface distribution
of Portuguese man-of-war (Physalia) in the
Caribbean, Gulf of Mexico, and the Florida Current (Gulf Stream). Schwartz and
This research has enjoyed long-term
support from many organizations and individuals. To name them all would require
space equal to a large portion of the paper.
Their assistance has had many forms, including administrative and supervisory
support, editorial assistance, egg collection, pen-rearing, and providing tag return data.
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ROSS WlTHAM
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