The intertubular compartment morphometry in capybaras (Hydrochoerus hydrochaeris) testis

The aim of the present study was to characterize the intertubule element volume density, individual and total Leydig cells volume, Leydig cell number per testis and per gram of testis, and leydigosomatic index in adult capybaras. Eight capybaras from a commercial abattoir were utilized. The intertubular compartment volume density and the Leydig cells were 45.2 and 31.13%, respectively. The individual and total Leydig cell volumes were 8.51 and 2169.41 x 10(-12) mL, respectively. The Leydig cell number per testis was 3.8 billion and the Leydig cell number per gram of testis was 126 million. The leydigosomatic index was 0.037%. In conclusion, this study shows that capybaras have one of the greatest individual and total Leydig cell volume and Leydig cell volume density, and that the Leydig cell number per gram of testis is at least double the mean for mammals previously investigated in its order.     

Using predator feces as a repellent for free-ranging urban capybaras (Hydrochoerus hydrochaeris)

acta ethologica - Biological repellents have been used as a control method to mitigate human-wildlife conflict worldwide. We aimed to evaluate the effect of jaguar (Panthera onca) feces as a...     

Seminiferous epithelium cycle and its duration in capybaras (Hydrochoerus hydrochaeris).

Although capybara is the largest rodent in the world and largely distributed in Central and South America, there is no report in the literature concerning the cycle of seminiferous epithelium in this species. In the present study, the length of spermatogenic cycle was estimated using intratesticular injections of tritiated thymidine. Animals were sacrificed at 1 h, 8 days, and 17 days after injections. The duration of one spermatogenic cycle in capybaras is 11.9 +/- 0.1 days (SEM). Spermatogenesis was estimated to last 53.6 days, when considering that the total duration of spermatogenesis takes about 4.5 cycles of seminiferous epithelium. The approximate life span of primary spermatocytes is 19.1 days, while spermiogenesis lasts 16.7 days. Staging in capybaras was based on the spermatid nuclei shape and location of spermatids, named tubular morphology method, which consists of 8 stages in all species. The relative stage frequencies in capybaras, based on the analysis of approximately 200 cross sections of seminiferous tubule for each of the ten animals were as follow: stage 1: 14.0 +/- 1.5%; stage 2: 15.1 +/- 1.0%; stage 3: 15.7 +/- 1.1%; stage 4: 14.6 +/- 1.1%; stage 5: 8.7 +/- 0.7%; stage 6: 7.0 +/- 0.7%; stage 7: 9.4 +/- 0.9%; stage 8: 15.5 +/- 1.0%. The pre-meiotic, meiotic and post-meiotic phases relative frequencies were 44.8%, 14.6% and 40.6%, respectively. Compared to most rodents investigated so far, the duration of spermatogenesis in capybaras is relatively long.     

Characterization of microsatellite markers from capybaras,Hydrochoerus hydrochaeris (Rodentia: Hydrochoeridae)

Fourteen microsatellite loci were isolated from capybaras (Hydrochoerus hydrochaeris), which are large, diurnal social rodents that occur in the wet savannas of South America. Five of these loci were monomorphic. The remaining nine loci were polymorphic (two to seven alleles per locus), with observed levels of heterozygosity ranging from 0.063 to 0.800 (n = 17 animals). The latter loci provide a valuable tool for assessing patterns of parentage and kinship within capybara social groups.     

Genetic structure of a group of capybaras, Hydrochoerus hydrochaeris (Rodentia: Hydrocheridae) in the Colombian Eastern Llanos

The capybaras are the biggest rodents in the world but, however, there are not extensive population genetics studies on them. In the current work, we studied the genetic structure of a troop of 31 capybaras (Hydrochoerus hydrochaeris) sampled in Hato Corozal, Casanare Department at the Colombian Eastern Llanos, by means of five microsatellite markers. The gene diversity was 0.61 and the average allele number was 5.2, which is a medium-low level for markers of this nature. Out five markers employed, three were in Hardy-Weinberg equilibrium meanwhile one showed a significant homozygote excess and other presented a significant heterozygote excess. There were not significant genetic differences between males and females inside this troop. The application of different procedures to determine possible historical demographic changes (population expansions or bottlenecks) clearly showed that the population analyzed crossed over a very narrow recent bottleneck. The illegal hunt is the possibly cause of this strong genetic bottleneck.     

Behavioral observations in a capybara colony (Hydrochoerus hydrochaeris)

Capybaras (Hydrochoerus hydrochaeris), the largest living rodents, are receiving increasing interest as an economically attractive source of meat and hides in tropical America. An unmanaged capybara colony was studied in a setting adjacent to agricultural activities in Brazil. Preliminary notes were made on alarm responses to intruders, various aspects of flight behavior, and investigatory activity. The findings were mostly consistent with studies carried out by other investigators, suggesting that capybara behavior is similar from one region to another. The animals have potential for habituation to humans and are probably good candidates for domestication. Expanded commercial exploitation of capybaras could benefit their survival and welfare as well as contributing to the preservation of neotropical ecology in general.     

Acute phase protein response in the capybara (Hydrochoerus hydrochaeris)

We evaluated the acute phase protein response in capybaras (Hydrochoerus hydrochaeris). Three animal groups were used: 1) healthy animals (n=30), 2) a group in which experimental inflammation with turpentine was induced (n=6), and 3) a group affected with sarcoptic scabies (n=14) in which 10 animals were treated with ivermectin. Haptoglobin (Hp), acid-soluble glycoprotein (ASG) and albumin were analyzed in all animals. In those treated with turpentine, Hp reached its maximum value at 2 wk with a 2.7-fold increase, whereas ASG increased 1.75-fold and albumin decreased 0.87-fold 1 wk after the induction of inflammation. Capybaras affected with sarcoptic scabies presented increases in Hp and ASG of 4.98- and 3.18-fold, respectively, and a 0.87-fold decrease in albumin, compared with healthy animals. Haptoglobin and ASG can be considered as moderate, positive acute phase proteins in capybaras because they showed less than 10-fold increases after an inflammatory process and reached their peak concentrations 1 wk after the induction of inflammation. Conversely, albumin can be considered a negative acute phase protein in capybaras because it showed a reduction in concentration after inflammatory stimulus.     

Surgical sterilization of free-ranging capybaras (Hydrochoerus hydrochaeris): “Passos Nunes” uterine horn ligature

Capybaras are the primary hosts of Amblyomma sculptum tick, vectors of Rickettsia rickettsia bacteria, and the zoonotic agent of Brazilian Spotted Fever (BSF). In this context, contraceptive methods have been suggested for population control in order to reduce the number of free-ranging capybaras cohabiting with humans in urban and rural areas and acting as disease amplifiers. To maintain the group''s expected behavior and social hierarchy, sterilization techniques that preserve the gonads are recommended. On 126 female capybaras in the Brazilian state of São Paulo, a new surgical technique named “Passos Nunes” uterine horn ligature was performed after adequate general anesthesia. It achieved effective surgical sterilization, with an incision length of about 3 cm in the periumbilical linea alba, cranial to the pubis. After entering the abdominal cavity, the urinary bladder is pulled laterally to access the uterine horns and the cervix. The uterine horn is folded up, forming a strap; the distal portion of the strap is ligated and its distal end sectioned. The exact process is performed on the opposite horn. After the surgical procedure, the musculature is sutured in a sultan pattern and the subcutaneous tissue with a horizontal mattress pattern. The skin is sutured in a separate simple format, using nylon 2.0 for all steps. The wide exposure of the uterine horns facilitates the confirmation of pregnancy, allowing the surgeon to choose between salpingo hysterectomy or ligature of the uterine horns. The present study presents a new technique of surgical sterilization that can be used in female free-ranging mammals in which maintenance of the gonads is recommended, and births of offspring should not occur.     

Capybara (Hydrochoerus hydrochaeris) distribution in agroecosystems: a cross-scale habitat analysis

Aim The aim of this study was to understand the spatial distribution of capybara (Hydrochoerus hydrochaeris) according to habitat attributes, using a multiscale approach based on fine‐ and broad‐scale variables in agroecosystems. Location Piracicaba river basin, south‐eastern Brazil (22°00′–23°30′ S; 45°45′–48°30′ W). Methods Potential habitats for capybara were selected in order to evaluate species presence/absence from October 2001 to December 2002. In each site, habitat attributes were sampled in the field (fine scale) and from GIS maps (broad scale) in terms of their presence or absence close to water. The variability of land cover between study sites was described by principal components analysis. Chi‐square tests were calculated for capybara presence/absence and the presence of each habitat attribute. A linear discriminant function analysis was used to describe to what extent the species’ presence could be explained by habitat attributes. Results The species presence was predominantly related to flat open areas (slope ranging from 0% to 6%) (χ² = 37.054, d.f. = 4, P < 0.001), covered by sugar cane or cultivated pasture (χ² = 84.814, d.f. = 9, P < 0.001). Terrain curvature, water meadows, aquatic vegetation, forest cover and open areas resulted in the best combination of variables, explaining 69.7% of capybara occurrence in the study sites in this river basin. Main conclusions Capybaras are widespread in the Piracicaba river basin, except in elevated areas. The spatial distribution of capybara was associated with the main types of land cover in the river basin – sugar cane plantations or pasture – both key food sources for capybara. This probably explains the species’ recent abundance in the region, since an intensive process of landscape alteration has taken place in this region owing to the expansion of agriculture in recent decades. These results may be useful in understanding the relationship between recent landscape modifications and the species’ population expansion in agroecosystems.     

The capybara (Hydrochoerus hydrochaeris) as a reservoir host for Trypanosoma evansi

Discovery of two ill horses and three dogs naturally infected with Trypanosoma evansi near an experimental station in the Eastern Plains of Colombia led to a search for reservoir hosts of the parasite. Infection was detected in 8/33 healthy capybaras (Hydrochoerus hydrochaeris), none of the remaining 14 horses, and none of 32 Zebu cattle (Bos indicus), 18 paca (Cuniculus paca) and 20 spiny rats (Proechimys sp.). Contrary to common opinion, the results indicated a carrier state in the capybara. Diagnosis was based on morphology, behaviour in albino rats, and pathogenicity and host range in domestic animals.     

Evaluation of three immobilization combinations in the capybara (Hydrochoerus hydrochaeris)

Capybaras (Hydrochoerus hydrochaeris) are the world's largest rodent. Owing to its uniqueness, 50 AZA institutions in North America display this species. As shown by a survey, no standard anesthetic protocol has been developed for this species. As a part of an ongoing behavioral study in Venezuela, capybaras were surgically implanted with radio transmitters. Animals were randomly assigned to one of the three immobilization protocols: (1) Tiletamine HCl/Zolazepam HCl, (2) Tiletamine HCl/Zolazepam HCl/Medetomidine HCl, and (3) Tiletamine HCl/Zolazepam HCl/Medetomidine HCl/Butorphanol tartrate. The protocol recommended for minimally invasive procedures when inhalant anesthetics are unavailable is a combination of Tiletamine HCl/Zolazepam HCl/Medetomidine HCl/Butorphanol tartrate. This is based on ease of administration, volume, onset of action, depth of anesthetic achieved, reversibility, safety, and costs. Zoo Biol 29:59–67, 2010. © 2009 Wiley‐Liss, Inc.     

The Function of Click Call Emission in Capybaras (Hydrochoerus hydrochaeris)

Contact calls are used to promote cohesion among individuals that live in social groups. Capybaras are very gregarious and often vocalize. This species emits a vocalization known as a click, which has been observed during aggregating and foraging behaviors, suggesting contact or monitoring call function. We carried out a playback experiment to evaluate behavioral responses to the capybara's click call and to a bird call, used as control in ten capybaras. We compared animals' latency to respond to stimuli, the time spent in behavioral patterns, alertness, head orientation toward the sound source, and approach to the sound source. All capybaras responded to the emission of the click call playback. Most of them assumed an alert position, showed head orientation toward the sound source, and approached the sound source. They promptly reacted to the first click call emission, while few reacted to the first bird call emission, used as control. All subjects showed behavioral changes after the second emission of the click call, and some responded to the third emission. Just three individuals answered after the first control emission, while none of them responded to the second and third emission of the playback. Therefore, click call playback promotes prompt behavioral changes in capybaras, including approach to the sound source. These results indicate that this vocalization functions as a contact or monitoring call in the species.     

Rumen ophryoscolecid protozoa in the hindgut of the capybara (Hydrochoerus hydrochaeris)

Rumen ophryoscolecid protozoa were observed in feces obtained from two capybara (Hydrochoerus hydrochaeris) housed at the Columbus Zoo, Columbus, Ohio. Total numbers were 58.1 X 10(4) and 19.0 X 10(4) per gram of wet feces in a male and female capybara, respectively. Four common rumen species of Entodinium were observed in the feces from both animals, with low numbers of Eudiplodinium maggii and Elytroplastron bubali also occurring in the male. Establishment of rumen ophryoscolecid ciliates in the intestinal tract of non-ruminant herbivores has not been reported previously.     

Cross checking censuses and a model of the annual cycle of mortality and reproduction in capybaras (Hydrochaeris hydrochaeris)

Improved management of capybaras (Hydrochaeris hydrochaeris) for meat and hide production requires better knowledge of the status of the population throughout the year, its density, as well as monthly rates of mortality and reproduction. This study was made on 50,500 ha of a ranch in the Llanos of Venezuela. A model of the annual cycle of mortality and reproduction of a hypothetical population of 50,000 capybaras was constructed, based on age composition information from 1,269 capybaras harvested in March over a period of 7 years. Age was determined by the lens technique and the growth curve of the lens and a table of lens weights and corresponding age are presented. Because censuses of wildlife are dependent on assumptions which frequently are fulfilled to an unknown degree and fiducial limits may be large, here three cross checking censuses were made. The censuses varied from 3 to 8% of their mean. The analytical model predicted a 26.02% reduction of the population during the 2 months when the annual harvest occurred and the strip censuses showed a reduction of 27.63%, a degree of agreement lending credibility to both the model and the censuses. A table of the annual cycle of births based on age composition of a cohort of 358 capybaras is presented showing births throughout the year but with a peak in September and 56% being born from August to November. The mean monthly probability of dying for adult capybaras was calculated to be 0.075 based on a sample of 1.199 animals greater than 12 months old. The oldest capybaras were estimated to be 5 years of age.     

Vascular damage caused by Cruorifilaria tuberocauda in the capybara (Hydrochoerus hydrochaeris)

Infection with Cruorifilaria tuberocauda caused vascular damage in the kidneys, lungs and heart of the capybara (Hydrochoerus hydrochaeris). The most significant lesions observed were in the renal and pulmonary arteries. They consisted of villous endarteritis, intimal and medial hypertrophy of the vessel walls, and large rugose protuberances that encroached upon the lumen leading to pyramidal infarcts in the kidneys. Coronary vascular lesions were related to dead and calcified parasites.     

Histopathology of Tick-Bite Lesions in Naturally Infested Capybaras (Hydrochoerus hydrochaeris) in Brazil

In the present work features of tick-bite lesions were evaluated in capybaras naturally infested with Amblyomma cajennense and Amblyomma dubitatum ticks. Gross appearance of tick bite site was characterized by a mild swelling and erythema. Microscopic examination revealed the cement cone, a tube-like homogenous eosinophilic mass penetrating deep into the dermis. This structure was surrounded in the dermis by a cellular infiltrate and free eosinophilic granules and was associated to edema of variable intensity. Necrosis was a common feature deep in the dermis particularly at the far end of the eosinophilic tube. Hyperplasia, cellular edema and occasionally necrosis of keratinocytes could be seen at both sides of the ruptured epidermis. Cellular infiltrate was constituted overwhelmingly by polymorphonuclear leukocytes with eosinophilic granules. In capybaras cells with such features can be either eosinophils or heterophils (pseudoeosinophils), the latter being the equivalent of neutrophils of other mammals. Ultrastructural analysis of the cellular infiltrate revealed the predominance of heterophils over eosinophils. Mononuclear cells and mast cells and, in lesser numbers, basophils were also seen at skin attachment sites. The presence of heterophils in the reaction of capybaras against Amblyomma ticks is an outstanding feature but its role in the reaction to the tick is not known. It is however speculated that capybara heterophils might be associated with a more permissive environment for tick feeding and pathogen transmission as already shown for the equivalent cell type, the neutrophil, in the reaction of the dog against the Rhipicephalus sanguineus tick.     

Assessment of capybara (Hydrochoerus hydrochaeris) populations in the wetlands of Corrientes,Argentina

Ten sampling sites were selected to represent six distinct habitat types used by capybaras (clean lagoons, dirty lagoons, cutwaters, fens and marshes, gallery forests, and erosion ditches). The sites were sampled during winter (July and August); densities were expressed as number of capybaras per linear km of shoreline (C/LKS). The sites were classified as protected from poachers (P), under light hunting pressure (LHP), and under heavy hunting pressure (HHP). Clean protected (P) lagoons had three times as many capybaras as LHP ones (30.7 and 10.9 C/LKS, respectively), and thirty times those under HHP (1.0 C/LKS). Protected marshes and dirty lagoons had even higher capybara densities (52.5 and 50.0 C/LKS, respectively). Gallery forests under LHP had low densities (6.3 C/LKS), and protected cutwaters intermediate densities (27.5 C/LKS). Erosion ditches had exceptionally high densities (900 C/LKS), probably because cattle were fenced out, reducing forage competition. These densities, when converted to the standard unit area measurement (individuals/ha), were similar to those obtained by other researchers in the Brazilian Pantanal, and somewhat smaller than those in the Venezuelan Llanos. Mean number of capybaras per group remained relatively constant in all habitats (averages ranged between 9.2 and 11.8 individuals/group) but its coefficient of variation was much higher in LHP sites, probably because social structure was altered severely by hunting. The overall ratio of young to adults and juveniles was 1:7.4. In one of the sites, 13 of 34 groups (38.2%) were with young (average of 17 capybaras per group, 4.7 of which were young), confirming that this species can reproduce all year long.Requests for reprints should be sent to: Dr. J. Rabinovich.     

Rumen Ophryoscolecid Protozoa in the Hindgut of the Capybara (Hydrochoerus hydrochaeris)1

Rumen ophryoscolecid protozoa were observed in feces obtained from two capybara (Hydrochoerus hydrochaeris) housed at the Columbus Zoo, Columbus, Ohio. Total numbers were 58.1 times 10⁴ and 19.0 times 10⁴ per gram of wet feces in a male and female capybara, respectively. Four common rumen species of Entodinium were observed in the feces from both animals, with low numbers of Eudiplodinium maggii and Elytroplastron bubali also occurring in the male. Establishment of rumen ophryoscolecid ciliates in the intestinal tract of non-ruminant herbivores has not been reported previously.