Catchment-specific element signatures in estuarine crocodiles (Crocodylus porosus) from the Alligator Rivers Region, northern Australia

The concentrations of Na, K, Ca, Mg, Ba, Sr, Fe, Al, Mn, Zn, Pb, Cu, Ni, Cr, Co, Se, U and Ti were determined in the osteoderms and/or flesh of estuarine crocodiles (Crocodylus porosus) captured in three adjacent catchments within the Alligator Rivers Region (ARR) of northern Australia. Results from multivariate analysis of variance showed that when all metals were considered simultaneously, catchment effects were significant (P≤0.05). Despite considerable within-catchment variability, linear discriminant analysis (LDA) showed that differences in elemental signatures in the osteoderms and/or flesh of C. porosus amongst the catchments were sufficient to classify individuals accurately to their catchment of occurrence. Using cross-validation, the accuracy of classifying a crocodile to its catchment of occurrence was 76% for osteoderms and 60% for flesh. These data suggest that osteoderms provide better predictive accuracy than flesh for discriminating crocodiles amongst catchments. There was no advantage in combining the osteoderm and flesh results to increase the accuracy of classification (i.e. 67%). Based on the discriminant function coefficients for the osteoderm data, Ca, Co, Mg and U were the most important elements for discriminating amongst the three catchments. For flesh data, Ca, K, Mg, Na, Ni and Pb were the most important metals for discriminating amongst the catchments. Reasons for differences in the elemental signatures of crocodiles between catchments are generally not interpretable, due to limited data on surface water and sediment chemistry of the catchments or chemical composition of dietary items of C. porosus. From a wildlife management perspective, the provenance or source catchment(s) of 'problem' crocodiles captured at settlements or recreational areas along the ARR coastline may be established using catchment-specific elemental signatures. If the incidence of problem crocodiles can be reduced in settled or recreational areas by effective management at their source, then public safety concerns about these predators may be moderated, as well as the cost of their capture and removal. Copyright © 2002 Elsevier Science B.V.

Diet and condition of American Alligators (Alligator mississippiensis)in three central Florida lakes

Understanding the diet of crocodilians is important because diet affects condition, behavior, growth, and reproduction. By examining the diet of crocodilians, valuable knowledge is gained about predator-prey interactions and prey utilization among habitats. In this study, I examined the diet and condition of adult American alligators (Alligator mississippiensis) in three central Florida lakes, Griffin, Apopka, and Woodruff. Two hundred adult alligators were captured and lavaged from March through October 2001, from April through October 2002, and from April through August 2003. Alligators ate a variety of vertebrate and invertebrate prey, but vertebrates were more abundant and fish dominated alligator diets in the lakes. Species composition of fish varied among the lakes. The majority of the diet of alligators from Lakes Apopka and Woodruff was fish, 90% and 84% respectively. Lake Apopka alligators consumed a significantly (P = 0.006) higher proportion of fish in their diet. Fish were 54% of the diet of Lake Griffin alligators and the infrequent occurrence of reptiles, mammals, birds, and amphibians often resulted in a large biomass. Differences in alligator diets among lakes may be due to differences in sample size (higher numbers of samples from Lake Griffin), prey availability, habitat, prey vulnerability, or prey size. Alligator condition (Fulton’s Condition Factor, K) was significantly (P < 0.001) different among the lakes. Alligators from Lake Apopka had the highest condition, followed by those from Lake Griffin, and alligators from Lake Woodruff had the lowest condition. Composition of fish along with diversity and equitability of fish in alligator diets may have contributed to differences in condition among lakes. Condition was probably also due to factors other than diet such as alligator hunting behavior, alligator density, or year-round optimal temperature that prolongs feeding. The observed diet and condition differences probably reflect both habitat differences and prey availability in these three lakes.

Alligator Diet in Relation to Alligator Mortality on Lake Griffin, FL

Alligator mississippiensis (American Alligators) demonstrated low hatchrate success and increased adult mortality on Lake Griffin, FL, between 1998 and 2003. Dying Lake Griffin alligators with symptoms of poor motor coordination were reported to show specific neurological impairment and brain lesions. Similar lesions were documented in salmonines that consumed clupeids with high thiaminase levels. Therefore, we investigated the diet of Lake Griffin alligators and compared it with alligator diets from two lakes that exhibited relatively low levels of unexplained alligator mortality to see if consumption of Dorosoma cepedianum (gizzard shad) could be correlated with patterns of mortality. Shad in both lakes Griffin and Apopka had high levels of thiaminase and Lake Apopka alligators were consuming greater amounts of shad relative to Lake Griffin without showing mortality rates similar to Lake Griffin alligators. Therefore, a relationship between shad consumption alone and alligator mortality is not supported.

Estimating Sighting Proportions of American Alligator Nests during Helicopter Survey

Proportions of American alligator (Alligator mississippiensis) nests sighted during aerial survey in Florida were estimated based upon multiple surveys by different observers. We compared sighting proportions across habitats, nesting seasons, and observer experience levels. The mean sighting proportion across all habitats and years was 0.736 (SE=0.024). Survey counts corrected by the mean sighting proportion reliably predicted total nest counts (R2=0.933). Sighting proportions did not differ by habitat type (P=0.668) or year P=0.328). Experienced observers detected a greater proportion of nests (Palligator nests when corrected by the appropriate sighting proportion.

Survival and Growth of American Alligator (Alligator mississippiensis) hatchlings after artificial incubation and repatriation

Hatchling American Alligators (Alligator mississippiensis) produced from artificially incubated wild eggs were returned to their natal areas (repatriated). We compared artificially incubated and repatriated hatchlings released within and outside the maternal alligator’s home range with naturally incubated hatchlings captured and released within the maternal alligator’s home range on Lake Apopka, Lake Griffin, and Orange Lake in Florida. We used probability of recapture and total length at approximately nine months after hatching as indices of survival and growth rates. Artificially incubated hatchlings released outside of the maternal alligator’s home range had lower recapture probabilities than either naturally incubated hatchlings or artificially incubated hatchlings released near the original nest site. Recapture probabilities of other treatments did not differ significantly. Artificially incubated hatchlings were approximately 6% shorter than naturally incubated hatchlings at approximately nine months after hatching. We concluded that repatriation of hatchlings probably would not have long-term effects on populations because of the resiliency of alligator populations to alterations of early age-class survival and growth rates of the magnitude that we observed. Repatriation of hatchlings may be an economical alternative to repatriation of older juveniles for population restoration. However, the location of release may affect subsequent survival and growth.

Why do Chinese alligators (Alligator sinensis) form bellowing choruses: A playback approach

Crocodilians are quite vocal relative to other reptile groups, and the alligators are among the most vocal of the crocodilians. The Chinese alligator, Alligator sinensis, is usually solitary but engages in bellowing choruses in certain waters during the mating season. This paper reports the organization of Chinese alligator's bellowing choruses based upon field observations and playback experiments. Alligators of both genders engaged in the choruses, remaining immobile throughout and inclining toward bellowing synchronously (i.e., starting and finishing at about the same time). The choruses lasted about 10 min with abrupt onset and offset. Moreover, playback experiments revealed that both male and female alligators responded equally to bellowing stimuli from the same and opposite sexes and that none of the tested alligators approached the loudspeaker in spite of playback of male or female stimuli. These suggest that Chinese alligators. may not bellow to compete for or attract mates during the choruses. Instead, when their ecological behaviors, namely, dispersed inhabitation, multi-copulation, restricted mating season, etc., are considered, we hypothesize that they may synchronize bellows to enhance group detectability for assembling individuals into certain waters for subsequent copulations. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3203667]

Response Specificity to Advertisement Vocalization in the Chinese Alligator (Alligator sinensis)

Stringency in the identification of conspecific call properties is essential among sympatric species to ensure conspecific mating, as the risk of improper recognition and heterospecific mating is high. In this study we investigated the basic signal structure required for intraspecies communication in the Chinese alligator (Alligator sinensis), a species that has no relatives living in sympatry, by playback of signals modified in the temporal (truncating original bellows with first 1/4, 1/2, 3/4 or last 1/4, 1/2, 3/4 portion) or frequency domain (with low- or high-pass filters at frequencies 100, 250, 500 and 1000 Hz), or by reversal of natural bellows. The playback experiments revealed that relatively large modifications in bellow temporal or frequency structure failed to impair Chinese alligators' bellowing behavior; even reversed bellows effectively evoked a positive response. In general, the first half of the bellow in temporal domain and frequencies below 500 Hz were critical for behavioral induction, while the last half of the bellow in temporal domain and frequencies above 500 Hz failed to produce a single positive response, implying a potential functional signal redundancy. The observed high tolerance to bellow variations in Chinese alligators may be an evolutionary adaptation to (1) the acoustic constraints of propagation imposed by dense vegetative habitats; or (2) a lack of selection pressure due to the low risk of incorrect conspecific recognition and heterospecific mating.

Acoustic signals of Chinese alligators (Alligator sinensis): Social communication

This paper reports the first systematic study of acoustic signals during social interactions of the Chinese alligator (Alligator sinensis). Sound pressure level (SPL) measurements revealed that Chinese alligators have an elaborate acoustic communication system with both long-distance signal-bellowing-and short-distance signals that include tooting, bubble blowing, hissing, mooing, head slapping and whining. Bellows have high SPL and appear to play an important role in the alligator's long range intercommunion. Sounds characterized by low SPL are short-distance signals used when alligators are in close spatial proximity to one another. The signal spectrographic analysis showed that the acoustic signals of Chinese alligators have a very low dominant frequency, less than 500 Hz. These frequencies are consistent with adaptation to a habitat with high density vegetation. Low dominant frequency sound attenuates less and could therefore cover a larger spatial range by diffraction in a densely vegetated environment relative to a higher dominant frequency sound. (C) 2007 Acoustical Society of America.

Synthesis and characterization of ferrocene-terminated ruthenium phenylacetylide complexes with alligator clips

Ferrocene-terminated trans/Ru(dppm)(2) (dppm=Ph2PCH2PPh2)-contained molecular wires with alligator clips were prepared. They are suitable for self-assembly on gold electrode to investigate the influence of metal incorporation on the electron transportation property of the molecular wires.

Alligator Creek S328

The South Carolina Department of Natural Resources provides maps to recreational and state shellfish grounds, available to the public for recreational harvesting or to commercial harvest. This map shows the location of Alligator Creek S328 Recreational Shellfish Ground in Charleston County.