The following copyrighted material cannot be copied for profit. You may however, use it for non-profit scholarly purposes. The proper citation is: Rivas, J. A. S. A. Aktay and R. Y. Owens. 2001. Paleosuchus trigonatus (Schneider’s Smooth-fronted Caiman) Nesting. Herpetological Review. 32(4): 251 Click here for a pdf
Paleosuchus trigonatus: Nesting. Natural history and nesting patterns of forest dwelling caimans is remarkably lacking due to the difficulty of finding and studying these animals in their remote habitats. In this contribution we document the characteristics, development and hatching of a nest found near the Tiputini river in the Ecuatorian amazon.
The nest was discovered on September 30, 1999 by serendipity walking in a sector of terra firme forest at least 2 Km away from the main river and 4.5 meters away from a shallow stream approximately 1 meter wide. The nest was at the bottom of a tree that had a broken branch producing a gap in the canopy. Thus, the nest was located under 81.54% canopy coverage in the spot of the area that received most direct sunlight.
The nest was built with decomposing leaf litter, small branches, and dirt. Small roots were found throughout, indicating that it was not recently constructed. The nest was of typical size for caimans, with diameters of 1.35 m and 1.45 m, and a height of 39 cm. The egg chamber was found in the center of the leaf pile and was 18 cm long, 22 cm wide, and 31 cm on its deepest part. The nest contained 16 fertile eggs that were on average 68.65 ± 3.3 cm long, 43.613 ± 0.610 cm wide and 73.750 ± 3.109 g in weight; and one infertile egg that was 50.8 cm long, 41.7 cm wide and 47 g. By the time of discovery, no band was evident when examining the eggs against a flashlight, but they were opaque enough to assume that the eggs were developing. The bands probably went all the way to the poles.
Day time temperature was monitored regularly during the first month showing an average of 27º C on the surface and 30º C at the egg chamber. On November 27 the nest was found to have hatched by one of our helpers. All the shells looked to have hatched successfully (the infertile egg was removed upon discovery). In the shells there were abundant ants that were eating the remains of blood and yolk attached to the shells, which suggests a very recent hatching (probably the former day at the earliest). On March the 19th of 2000 we found 5 juveniles babies dwarf caimans within 100 meters from the nest (see measurements in Table 1) and no other crocodilian was found in the creek.
The juveniles were found spread out in both directions of the creek, not clumped in a group and when they were caught they were very feisty and not prone to exhibit distress calls, unlike other juvenile caimans. Day and night surveys of the small creek as far as 500 meters in both directions failed to reveal the presence of any adult caiman suggesting that the female did not guard the nest or neonates.
It is hard to speculate about the survival of the clutch since after the hatching and prior to our discovery of the clutch there had been a large flood that could have moved the hatching down the river. However, tiger heron (Tigrisoma lineatum) does occur in the area and were often seen in this same habitat in hunting attitude. It is interesting that the place of the nest was right below the gap in the canopy such that it received direct sun during some hours of the day. Such combination of a gap in the canopy and proximity to a creek might be important cues that the female uses in order to built a successful nest taking advantage of direct sunlight for incubation of the eggs and proximity to a river that the offspring occupy upon hatching.
Acknowledgement: Data for this contribution were collected during the
activities, and as a byproduct, of a course of tropical ecology by
Jesús A. Rivas, Sevima A. Aktay, and Renee Y. Owens. Venezuela Nature tours,
Table 1. Measures of 5 juvenile Paleosuchus trigonatus found in the
|
Individual ID |
Weight (g) |
SVL (cm) |
TL (cm) |
HL (mm) |
HW (mm) |
|
Mean |
103 |
17.34 |
31.62 |
52.65 |
20.83 |
|
SD |
13.27 |
0.67 |
1.14 |
1.5 |
1.85 |
|
Min |
85 |
16.1 |
29.9 |
50.09 |
17.28 |
|
Max |
120 |
18 |
32.8 |
54.21 |
22.27 |