Attacks on Humans by Neotropical Otters

Abstract

Neotropical otters Lontra annectens (Carnivora, Mustelidae) are widely distributed in Central and South America. Studies on the behavior of this species are rare, resulting in the fact that its ethology is one of the lesser known among the mustelids. The Neotropical otter is considered solitary and territorial but not aggressive, and it generally shows a shy and elusive behavior. Here we described the first two documented cases of attack by Neotropical otters on humans. The first occurred in Sacatepéquez, Guatemala, and the second, in La Guajira, Colombia. Respectively, adult female and male humans were injured with differences in the severity of the wounds, clinical course, and outcomes. We recommend further research on the agonistic behavior of Neotropical otters. A protocol for attention to injuries caused by Neotropical otters is suggested.

Introduction

Neotropical otters Lontra annectens (Carnivora, Mustelidae), previously recognized as Lontra longicaudis annectes, ¹ are widely distributed in Central and South America. ² The species inhabits wetlands with abundant water bodies such as rivers, lagoons, marine shores, and creeks, sometimes in areas with a certain degree of anthropogenic impact. ³ Otters are top predators and successful carnivores, feeding on a wide variety of prey. Studies on the behavior of wild Neotropical otters are rare, making Neotropical otters some of the lesser understood species among the mustelids. ⁴ Adult Neotropical otters weight between 5 and 10 kg and measure 1.2 to 1.7 m in length, with the tail representing about a third of the total length, ³ which is the size of a small domestic dog. Additionally, otters have specialized teeth, including sharp canines and carnassials, and large crushing molars. ⁵ Hence, they are provided with the ability to inflict lethal bites to a prey or to a target victim. Otters mark latrine sites with spraint (feces) likely to establish and maintain territories ⁶ and aid in expressing hostility. ⁵ Despite its territorial behavior, this mustelid is not considered aggressive toward humans and generally shows a shy and elusive behavior. However, it has been reported to interact with fisheries activities and compete for fishing resources.^7–9 Here we describe the first documented nonfatal Neotropical otter attacks on humans occurring in Guatemala and Colombia (Figure 1).

Figure 1.

Locations of first documented cases of Neotropical otter attack on humans. A, In a Guatemalan facility. B, In a Colombian nature reserve.

Case Reports

Case 1

The first incident took place on October 12, 2012 at 1730 at San Bartolomé Milpas Altas, Sacatepéquez, Guatemala (14°36′45.4″ N/90°39′44.4″W) (Figure 1A). The bite was made by a 3-y-old solitary female Neotropical otter raised under human care in a zoo. It is believed that during the routine cleaning of her shelter, the otter was startled by an external noise and reacted by biting the right foot of her caretaker, a 19-y-old woman (Figure 2A). After the attack, a general doctor administrated local anesthesia to the patient and performed a thorough cleaning of the wound with chlorhexidine followed by a small amount of debridement of the tissue. The physician prescribed, alongside daily local cleaning, an antibiotic threatment of 20 mg·kg^–1 amoxicillin-clavulanic acid to be administered twice a day for 7 d. After 9 d, tissue necrosis, inflammation, and pain were observed (Figure 2B), and a second consulted doctor deemed it necessary to debride the necrotic tissue, a procedure performed under general anesthesia by a surgeon (Figure 2C). After debridement, a bandage was placed on the wound together with a hydrocolloidal patch (DuoDERM, CovaTec, Bridgewater, NJ) that would serve to generate granulation tissue and heal the wound by secondary intention. The first bandage was in place for 2 wk, and then it was changed once a week for 3 mo. The bandage change was made by the surgeon. At the fourth month, the bandage change was performed at home, only for the purpose of applying a healing cream. This dressing change lasted additional 3.5 mo until complete healing (Figure 2D, E).

Figure 2.

Case 1. Seventy days evolution of a wound inflicted by an adult female of Neotropical otter to an adult human female. A. October 12; B. October 21; C. November 18; D. December 11; E. December 21. See the text for explanations. Photos: G. González.

Case 2

On April 10, 2020, the researcher and coauthor AAG-V, a 32-year-old male at the time of the incident, visited La Reserva Forestal Protectora de Montes de Oca, Jordan, La Guajira, Northern Colombia, during his Neotropical otter monitoring activities. The incident took place at 900 at the Carraipia River (11°10′9.94′′ N/72°22′57.36′′W) (Figure 1B). AAG-V first detected the otter's vocalizations, and soon after, he was able to get a sighting of 2 Neotropical otter cubs. The otters were considered juvenile because they already had open eyes and were showing exploratory behavior on the shore of the river. No adult was detected at the time. AAG-V climbed a tree, searching for a better position to observe the animals, and took some photographies of them for about 5 min. Shortly after he descended from the tree, 3 adult Neotropical otters attacked him, biting his lower extremities and feet. During the attack, the otters constantly emitted vocalizations, including screams and growls. AAG-V escaped from the aggression by jumping and running and recalls kicking one of the otters. On examination, AAG-V had minor cuts with profuse bleeding in the skin of the heels as well as many superficial injuries on both feet (Figure 3). Due to the challenging geographic conditions where the incident occurred, no medical attention was provided. The person was not treated with antibiotics, rabies and tetanus vaccines, or stitches. Over the next 3 d after the attack, the wounds were thoroughly washed with soapy water and thereafter treated with Aloe vera bandages. The wounds healed satisfactorily, and the patient did not have any health complications after treatment.

Figure 3.

Case 2. Multiple lacerations and bite wounds inflicted on a man's feet by 3 wild adult Neotropical otters. Photos: A.A. González-Vargas.

Discussion

Belanger et al (2011) conducted a preliminary revision (pre-1980–2010) of anecdotical and published cases of otter attacks on humans, ¹⁰ and more recently, Morgan et al (2023) updated the review (2011–23). ¹¹ The results of both papers are consistent: Most of the attacks on humans by mustelids involved the North American river otter (Lontra canadiensis) and took place mostly in Florida. ¹² Other mustelid species involved in attacks to humans are smooth-coated otters Lutrogale perspicillata in India ¹³ and Eurasian otters Lutra lutra in Europe. Attacks by giant otters (Pteronura brasiliensis) have only been reported for specimens under human care. ¹¹ Two fishers interviewed in Tamaulipas, Mexico, claimed that a Neotropical otter nearly attacked them, and another described that an otter climbed onto his boat aggressively. ¹⁴ However, to our knowledge, there are no previous documented cases of L annectens attacking and harming humans.

In the cases presented here, the victims received prompt treatment. However, the female patient in Case 1 experienced a significantly more complicated and extended clinical course than the male patient in Case 2, whose wounds healed rapidly. Due to the numerous differences between Cases 1 and 2—such as environmental conditions, geographic location, characteristics of the individual otters, health of the victims, and types of treatment—it is challenging to determine why the injuries varied in outcome. For instance, the severity of a wound infection inflicted by a wild carnivorous mammal may be influenced by the oral bacteria of the biting animal (which also can be affected by the microbiome of their prey), the bacteria from the victim's own skin, and the conditions of the environment at the time the injury occurred. ¹⁵ More investigation on oral bacteria of otters would be informative.

A person attacked by otters, in the wild or in captivity, ¹⁶ must receive immediate and comprehensive medical attention, ¹² following standard protocols of care for mammal bites. All puncture wounds and lacerations should be treated with thorough irrigation, wound care, and dressing. In situ and early cleansing reduces the risk of bacterial infection and is effective in eliminating rabies and other viruses. ¹² If necessary, wounds should be sutured with the risk of infection, function, and cosmetic outcome in mind. Antibiotic coverage should be considered. Otters are potential vectors of rabies virus. ¹⁷ Hence, a dose of rabies immune globulin must be considered. ¹² Also, tetanus vaccination of the patient should be up to date, and tetanus immunoglobin potentially can be considered as part of the treatment.

The cases reported here evidence that otter agonistic behavior may be elicited during the intromission of a person into their territories (in the wild or under human care), as well as manipulation or proximity to them, as previously reported. ¹⁸ This also can happen during the capture of wild cubs to keep or trade them as pets, an illegal activity already documented in Colombia.^19,20 The vocal behavior of the otters reported in Case 2 consisted of long screams, which are described as being uttered in agonistic social contexts, particularly in a physical aggression context. ²¹ More research on Neotropical otter agonistic display is suggested, both under human care and in the wild.

Otter attacks are unusual, partly because otters do not perceive humans as prey or as a predator. However, wild otter-human conflicts can be further exacerbated by habitat loss and fragmentation and reductions in wild prey. The L annectens population is declining continentwide, ² and current threats include trade, illegal hunting, residential and commercial development, energy production and mining, human disturbance, pollution, and natural system modifications. Coexistence with humans is a key aspect of the conservation of otters, but this needs to be better explored, particularly in the wild.