Conservation of large predators has long been a challenge for biologists due to the limited information we have about their ecology, generally low numbers in the wild, large home ranges and the ...continuous expansion of human settlements. The American crocodile (Crocodylus acutus) is a typical apex predator, that has suffered from all of these characteristic problems, especially the latter one. Humans have had a major impact on the recovery of this species throughout its range, even though most of the countries it inhabits have banned hunting. The last decade has made it clear that in order to implement sound conservation and management programs, we must increase our understanding of crocodile spatial ecology. However, in only two countries where American crocodiles have telemetry studies even been published. Herein we have characterized the spatial ecology of C. acutus on Coiba Island, Panama, by radio-tracking (VHF transmitters) 24 individuals between 2010 and 2013, to determine movement patterns, home range, and habitat use. We have then compared our findings with those of previous studies to develop the most comprehensive assessment of American crocodile spatial ecology to date. Females showed a higher average movement distance (AMD) than males; similarly, adults showed a higher AMD than sub-adults and juveniles. However, males exhibited larger home ranges than females, and concomitantly sub-adults had larger home ranges than juveniles, hatchlings, and adults. There was an obvious relationship between seasonal precipitation and AMD, with increased AMD in the dry and "low-wet" seasons, and reduced AMD during the "true" wet season. We found disaggregate distributions according to age groups throughout the 9 habitat types in the study area; adults and hatchlings inhabited fewer habitat types than juveniles and sub-adults. These sex- and age-group discrepancies in movement and habitat choice are likely due to the influences of reproductive biology and Coiba's precipitation cycle. Juveniles also showed distinct movement patterns and home ranges; however, with sexual maturation and development, these behaviors became more characteristic of adults and sub-adults. Ours is one of a very small number of studies that will allow future management and conservation planning to be based on the comprehensive integration of the spatial ecology of a Neotropical crocodylian apex predator.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Conservation of large predator species has historically been a challenge because they often overlap in resource utilization with humans; furthermore, there is a general lack of in-depth knowledge of ...their ecology and natural history. We assessed the conservation status of the Orinoco crocodile (Crocodylus intermedius), defining regional habitat priorities/crocodile conservation units (RHP/CCU) and regional research priorities (RRP) for this species. We also estimated a species distribution model (SDM) to define current suitable areas where the species might inhabit and/or that might be successfully colonized. The SDM area obtained with a suitable habitat probability ≥ 0.5 was 23,621 km2. Out of 2,562 km2 are included within protected areas in both Colombia (1,643 km2) and Venezuela (919 km2), which represents only 10.8% of C. intermedius' potential range. Areas such as Laguna de Chigüichigüe (flood plain lagoon) exhibited an increase in population abundance. In contrast, localities such as the Cojedes and Manapire Rivers reported a significant reduction in relative abundance values. In Colombia, disparity in previous survey methods prevented accurate estimation of population trends. Only one study in this country described an increase over a 13 years span in the Ele, Lipa, and Cravo Norte River populations based on nest surveys. We defined 34 critical areas (16 in Colombia, 17 in Venezuela, and one covering both countries) where we need to preserve/research/monitor and/or generate management actions, 10 RHP/CCU (six from Venezuela and four from Colombia) and 24 RRP (11 from Venezuela, 12 from Colombia, and one in both countries). Caño Guaritico (Creek) and the Capanaparo River in Venezuela and the Ele, Lipa, Cravo Norte River System and the Guayabero River in Colombia were defined as areas with the most optimal conditions for long-term preservation and maintenance of C. intermedius populations. We conclude that the conservation status of this species is still critical, which implies the necessity to increase efforts to recover the species, especially in Colombia, to guarantee its survival as a structural and functional component of the ecosystems it inhabits.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recently, the phylogenetic placement of the African slender snouted crocodile,
Crocodylus cataphractus, has come under scrutiny and herein we address this issue using molecular and morphological ...techniques. Although it is often recognized as being a “basal” form, morphological studies have traditionally placed
C. cataphractus within the genus
Crocodylus, while molecular studies have suggested that
C. cataphractus is very distinct from other
Crocodylus. To address the relationship of this species to its congeners we have sequenced portions of two nuclear genes (
C-mos 302
bp and ODC 294
bp), and two mitochondrial genes (
ND6-tRNA
glu
-
cytB 347
bp and control region 457
bp). Analyses of these molecular datasets, both as individual gene sequences and as concatenated sequences, support the hypothesis that
C. cataphractus is not a member of
Crocodylus or
Osteolaemus. Examination of 165 morphological characters supports and strengthens our resurrection of an historic genus,
Mecistops (Gray 1844) for
cataphractus.
The extant crocodylians comprise 23 species divided among three families, Alligatoridae, Crocodylidae, and Gavialidae. Currently, based on morphological data sets,
Tomistoma schlegelii (false ...gharial) is placed within the family Crocodylidae. Molecular data sets consistently support a sister-taxon relationship of
T. schlegelii with
Gavialis gangeticus (Indian Gharial), which is the sole species in Gavialidae. To elucidate the placement of
T. schlegelii within the extant crocodylians, we have sequenced 352
bp of the dentin matrix protein 1 (
DMP1) nuclear gene in 30 individuals and 424
bp of the nuclear gene
C-mos in 74 individuals. Molecular analysis of the
DMP1 data set indicates that it is highly conserved within the Crocodylia. Of special note is a seven base-pair indel (GTGCTTT) shared by
T. schlegelii and
G. gangeticus, that is absent in the genus
Crocodylus,
Osteolaemus, and
Mecistops. To date,
C-mos is the largest molecular data set analyzed for any crocodylian study including multiple samples from all representatives of the eight extant genera. Analysis of these molecular data sets, both as individual gene sequences and concatenated sequences, support the hypothesis that
T. schlegelii should be placed within the family Gavialidae.
The quantitative immunological technique of microcomplement fixation was used to examine serum albumin evolution among members of the order Crocodylia. The cross-reactivity of the albumin antisera ...and antigens employed in this study had been examined previously using the qualitative technique of immunodiffusion. The phylogenetic conclusions derived from these two data sets are highly congruent, including support of the families Alligatoridae and Crocodylidae, with the placement of Gavialis as the sister taxon of Tomistoma. Both methods provide similar information on the relative amounts of amino acid sequence divergence between albumin molecules; however, the data obtained from microcomplement fixation comparisons are more discriminating than those derived from immunodiffusion. The estimated divergence times within the Crocodylia derived from the fossil record are examined in light of divergence times predicted by the microcomplement fixation-based albumin clock. The traditional phylogenetic placement of Gavialis outside the remaining extant crocodilians is inconsistent with all molecular data sets and we suggest that a careful reexamination of both the extant and the fossil morphological data is warranted.
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