The male crocodylian phallus, an intromittent organ, transfers sperm to the female cloaca during reproduction. During copulation, the distal phallic glans inflates via blood-filled spongiform tissues; it enlarges into an elaborate shape that directly interacts with the female urodeum—the cloacal chamber that contains the female reproductive tract openings. Alas, the specific mechanics of crocodylian insemination and gamete transfer remain unclear. To that end, we investigated the gross and cellular morphology of the Nile crocodile (Crocodylus niloticus) glans characterizing tissues types and structural morphologies to better predict how these male tissues may interact with those of the female. We tracked blood flow from the descending aorta to the phallic glans by way of sulcus spermaticus-adjacent blood vessels. Utilizing an artificial inflation technique, we documented how the glans tissue shape changes with increased hydrostatic pressure in spongiform tissues including increases in height and width and the enlargement of a cup-like distal lumen. Sectioning the glans, we traced the decrease in dense collective tissues and the proliferation of inflatable tissues moving from proximal to distal. Concomitant with the development of the inflatable glans, we identified elastin-rich tissues around the inflatable glans regions and the deep sulcus spermaticus semen conduit. Together, these observations demonstrated the dynamic nature of the tissues, where collagen fibers supply mechanical strength and elastin fibers provide resilience and recoil. We hypothesize how these glans characteristics may interact with female tissues during copulation to increase the chance of successful gamete transfer.

Body condition (BC) has been used extensively to evaluate fitness in animals. In traditional studies of crocodiles, the paradigm of evaluating BC with the Fulton index and interpreting the results with quartiles is predominant. However, the wide variety of indices available provides a diversity of tools with which BC can be interpreted in multiple ways. In this study, three indices based on the function of length and weight were evaluated: the Fulton index (K), relative condition index (Kn), and scaled mass index (SMI). The body condition score (BCS) index was also adapted. This was performed as a clinical evaluation of specific morpho-anatomical points. The Fulton index presented a strong relationship with corporal size that generates poor interpretation, scoring low BC in small individuals and high BC in large individuals. This problem does not occur in Kn, SMI nor BCS. SMI and Kn are difficult to interpret, but this is normally conducted by quartiles, generating ambiguous and potentially misleading explanations. The use of BCS avoids these complications because its direct and simple evaluation acts to convert the abstract numbers of the indices to a clinical reality.

Information on the home range and movement patterns of Neotropical crocodilians is scarce for most species, despite being essential for developing management and conservation plans. The broad-snouted caiman (Caiman latirostris) is a Neotropical crocodilian with a wide geographical distribution in South America. This species inhabits artificial reservoirs (e.g., small weirs) in silvicultural areas. However, its use of space in such circumstances is still unknown. The present study aims to estimate home range and movement patterns of the broad-snouted caiman in a silviculture-dominated landscape in São Paulo state, southeastern Brazil. Eight adult caimans (four males and four females) were monitored by radiotelemetry (GPS-UHF system) from February 2010 to October 2011. The collected position points were used to estimate home range sizes and movement patterns. Mean home range size (± SD) of all individuals was 96.6 ± 183.9 ha and 43.2 ± 78.6 ha estimated by Minimum Convex Polygon (MPC) and 95% Kernel Density Estimate methods (KDE), respectively, without difference between the sexes. Individual mean daily movement was 37.6 ± 18.6 m/d, being greater during the reproductive period. The surrounding matrix formed by Eucalyptus plantations was relatively permeable to caiman movement. The present results suggest that the wide variation in the home range size of the broad-snouted caiman could be a result of the space-time distribution of resources and social interactions. Further, variations in environment temperature and reproductive activities can influence the movement pattern of the species. Future studies of crocodilians in agricultural landscapes should prioritize other dimensions possibly related to space use such as agricultural practices of the matrix, water contamination by agrochemicals, and hunting pressures.

The habitat of crocodiles (Crocodylus acutus) and caimans (Caiman crocodilus) has been subjected to pressure due to human expansion. Habitat reduction, coupled with the simultaneous growth of the crocodile population, increases the number of interactions between crocodiles and humans. There is currently no official and systematized interactions database, but it is necessary to know the magnitude and nature of the interactions and establish management measures. The objective of the work was to systematize and evaluate the interactions between crocodiles and humans in Costa Rica. Historical information was collected from several sources. A total of 99 records, dated between 1990–2017, were found from press reports and the Integrated System for Processing Environmental Complaints of the Ministry of Environment and Energy (SITADA). The Fire Department recorded 123 events in 2017. All Fire Department records corresponded to encounters or sightings. Of the SITADA incident records, 35.4% were non-fatal, 27.3% were fatal, 21.2% were encounters and sightings, and the remaining 16.1% were miscellaneous situations. Most interactions occurred during the day, a fact potentially explained by human behavior of being in bodies of water or on adjacent shoreline while the sun is out. Most interactions occurred in the Central Pacific, followed by the Caribbean and then the South Pacific. The information available is brief but allows to establish management measures. The country needs to create a national database of interactions and to encourage individuals to report their interactions. Further research should continue to analyze the data for trends with the goal of building recommendations to prevent an increase in negative interactions.

We describe body growth functions of broad-snouted caimans (Caiman latirostris) for wild and reintroduced individuals. Snout–vent length (SVL, cm) and age of young individuals and adult females were recorded for two different groups: (Py) animals born in the Proyecto Yacaré ranching program, from eggs collected in the wild; and (Wy) wild caimans Class I (< 25 cm SVL) whose age was determined by Size Frequency Analysis, plus females reintroduced by the Proyecto Yacaré and subsequently recaptured at reproductive age. To describe body growth, we adjusted five models through non-linear regression: Logistic, 4-Parameter Logistic (4-PL), Gompertz, 4-Parameter Gompertz (4-G), and von Bertalanffy. Each group was analyzed separately (Py and Wy), and we selected the most parsimonious model based on the Akaike criterion. We also analyzed the possible linear growth difference using ANCOVA. For Py, the Logistic model was best, whereas for Wy the most suitable was 4-PL, in which wild animals would arrive at the inflexion point 1.4 years later on average than in Py. Analyzing the stage at which their development was linear in shape, we detected that the wild animals had a similar growth rate to reintroduced individuals. As a result, although Py animals had experienced accelerated development whilst in captivity, it did not modify their subsequent growth in the wild. The likelihood of survival in this species increases with body size, thus it is important to emphasize that reintroduced animals are larger than wild animals of the same age and that previous farming conditions seem not to affect their growth in the wild. Therefore, we expect that reintroduced caimans will exhibit greater survivorship than natural animals of the same age. Consequently, an adjustment of the current ranching program should be considered, in the sense that population viability could be achieved by reintroducing a lower number of caimans each season.

The main goal of this research was to identify the hard ticks (Acari: Ixodidae) found in 10 individuals of spectacled caiman (Caiman crocodilus fuscus) from 349 individuals captured at the Hidroprado hydroelectric dam in the Department of Tolima, Colombia. Parasite prevalence was 2.9%. A total of 40 ticks were collected and two species identified: Amblyomma dissimile (n = 39) and Rhipicephalus sanguineus (n = 1). This is the second record of A. dissimile in C. crocodilus in Colombia and the first record of R. sanguineus in crocodilians. The natural infection of C. c. fuscus by A. dissimile establishes this species as a host in the life cycle of this tick. Similarly, parasitism by R. sanguineus indicates C. c. fuscus as a potential host for this tick, which is important since it is associated with domestic animals and has a high potential for transmission of zoonotic diseases. Our results highlight the parasitic relationship between ticks and one of the most resistant wild vertebrates: caimans. The prevalence, although not high, establishes the potential of ticks to parasitize different species and to be a vector of diseases for new groups of hosts.

Sexual identification of crocodilians is important in population studies and provides useful information for conservation and management plans and monitoring populations over time. It is possible to distinguish between male and female Caiman latirostris by cloacal palpation or eversion of the penis in individuals larger than 75 cm total length, but smaller animals possess a barely differentiable cliteropenis. In hatchlings, sex determination methods involve surgical examination, necropsy, or analysis of cranial dimorphism, which cannot be applied in the field. We classified hatchlings of C. latirostris by observing the color and shape of their genitals. The penis is a milky white organ with a rounded shape at the tip and a purple hue at the end, whereas the clitoris is shorter, whitish, and has a pointed end. The procedure was tested on hatchlings from three nests at the “Proyecto Yacaré” study area (Santa Fe province); half of the eggs of each nest were incubated at a constant temperature of 31°C (producing females) and the other half at 33°C (producing males). To observe the sexual organs by cloacal inspection, we used a modified instrument whose function during palpation is like that of a finger applied in large animals to evert the penis or clitoris. In the first days after hatching we correctly scored the sex of 80% of the individuals. The number of correct identifications was slightly lower for males than for females. This technique might be a useful tool for field studies, as it allows the sex of small caimans to be estimated in situ.