Technical Report
Hand-Rearing and Rehabilitation of
Orphaned Wild Giant Otters, Pteronura
brasiliensis, on the Rupununi River,
Guyana, South America
Diane McTurk1 and Lucy Spelman2n
1Karanambu Trust, Guyana, South America
2National Zoological Park, Smithsonian Institution, Washington, DC
From 1985?2003, 34 orphaned giant otters, Pteronura brasiliensis, (22 males, 12
females) were hand raised for eventual return to the wild at The Karanambu
Cattle Company Limited Ranch (Karanambu), on the Rupununi River, Guyana,
South America. The orphans ranged in age from 2 weeks to 9 months old; most
were 8?10-week-old cubs. Feeding, housing, exercising, veterinary care, and
rehabilitation protocols for young giant otters were developed during this period.
Six cubs died during hand-rearing; of these, four died from illness or injury, and
two were killed, one by a caiman and one by another orphaned otter. Of 34 giant
otters brought to Karanambu, 28 (82%) were reared successfully to an age and
condition suitable for rehabilitation, and 18 (53%) returned to the wild. Ten
otters survived hand-rearing but died either before or during the process of
rehabilitation. These hand-reared giant otters were killed by people (3 known,
2 presumed) or other giant otters (5), including one male otter that remained at
Karanambu for several years. During rehabilitation, young giant otters chose to
spend increasing amounts of time on the Rupununi River away from human care,
often interacting with wild giant otters. Although long-term monitoring was not
possible, Karanambu staff observed most (15 of 18) of the rehabilitated otters
repeatedly, for as long as 4 years after their return to the river. The giant
otter rehabilitation program at Karanambu generated new knowledge about
this species, and offered visitors the opportunity to observe them. Zoo Biol
24:153?167, 2005. 
c 2005 Wiley-Liss, Inc.
nCorrespondence to: Dr. Lucy Spelman, 3620 39th St., Apt F540, Washington, DC 20016.
E-mail: lucy.spelman@gmail.com
Received 16 June 2004; Accepted 16 September 2004
DOI 10.1002/zoo.20042
Published online in Wiley InterScience (www.interscience.wiley.com).
Zoo Biology 24:153?167 (2005)

c 2005 Wiley-Liss, Inc.
INTRODUCTION
In 2000, the giant otter (Pteronura brasiliensis) was moved from vulnerable to
endangered on the species list maintained by the World Conservation Union (IUCN)
[Foster-Turley et al., 1990]. Giant otters are endangered throughout most of their
range [Duplaix, 1980; Melquist, 1984; Mason and Macdonald, 1986; Foster-Turley
et al., 1990; Carter and Rosas, 1997; Schenck and Staib, 1998; Olson et al., 2001].
There are no current population estimates for giant otters in Guyana, where they are
known to range along river and lake systems. They are most numerous in
uninhabited areas [Groenendijk, 1998]. Along the Rupununi River and its
tributaries, where they are known as ??water dogs?? or ?turara? in Macusi language,
giant otters are often observed (G. Watkins, N. Duplaix, D. DeFreitas, A. Holland,
personal communication).
Human activity is the main threat to the giant otter along the Rupununi River.
In the absence of alluvial gold mining, the greatest disturbance is caused by ?re used
to clear paths along the high river banks. Burning and clearing of vegetation disturbs
the areas where giant otters excavate their hidden dens. A family group of giant
otters can consume large amounts of ?sh at a single feeding. They are often perceived
as competitors by human populations who rely on river ?sh as a source of food and
income [Gomez and Jorgenson, 1999]. Large, vocal, bold, and gregarious, giant
otters are easily captured or killed.
The Karanambu Cattle Company Limited Ranch (Karanambu) located on the
Rupununi River in southwestern Guyana, was established in 1927. Well known for
its relative abundance of wildlife, the ranch became a rehabilitation center for
orphaned wild giant otters in 1985. The Karanambu Trust, a nonpro?t organization,
was established in 1996 to promote environmental and wildlife research, conserva-
tion and education, with a focus on the giant otter. One of the organization?s initial
objectives was to develop protocols for hand-rearing young giant otters, with the
ultimate goal of returning them successfully to the wild on the Rupununi River. The
ranch property is ideally situated for this purpose because it includes and is
surrounded by giant otter habitat. Residents and visitors to Karanambu, local,
national and international, have a unique opportunity to observe and study wild
giant otters in their natural habitat.
MATERIALS AND METHODS
A retrospective survey of the records available for individual orphaned giant
otters brought to The Karanambu Cattle Company Limited Ranch (Karanambu)
during the years 1985?2002 formed the basis of this study.
The giant otters were cared for by the staff at Karanambu ranch, which covers
a total of 32,375 hectares (125 sq miles) including Kwaimatta village and
approximately 40 km (25 miles) of river frontage stretching along the left bank of
the Rupununi River between Massara and Yupukari villages. Approximately 100
people live on Karanambu, along with 600 cattle (longhorn-Brahman cross), and 30
working horses. More than 1,100 people live in two nearby Amerindian villages
(Yupukari and Massara). A narrow band of low gallery forest, followed by scrub
and savannah, borders each side of the river in this region and there are numerous
154 McTurk and Spelman
creeks, ponds, and oxbow lakes that vary in size between wet and dry seasons. Many
of the small creeks and ponds dry completely.
Between 1985?2002, 34 young, orphaned, wild, giant otters were brought to
Karanambu for hand-rearing and eventual rehabilitation to the wild. From the start,
the aim was to rear the cubs to independence and return them to the Rupununi River
(rehabilitation). Informal notes including details of husbandry (feeding, housing,
exercising, health problems) and rehabilitation were maintained on each giant otter
beginning in 1985; formal veterinary records were maintained beginning in 1996. All
notes were reviewed retrospectively, and organized into three stages: arrival, hand-
rearing, and rehabilitation.
Information was gathered and summarized for each stage. Arrival infor-
mation included date, location found, age, sex, weight, and health status upon
arrival. Hand-rearing information included survival, details of feeding, housing,
exercise, management of social interactions with other orphaned otters, and
medical care for injury or illness. Rehabilitation information included timing and
duration of interactions with other wild otters, sightings of orphaned otters
interacting with or joining packs of wild giant otters, evidence of reproductive
activity, and survival.
RESULTS
Arrival
Thirty-four young giant otters (22 males, 12 females) were brought to
Karanambu over an 18-year period (Table 1; note arrival dates include 1985?2002,
rehabilitation dates include 2003). The otters ranged in age from 2 weeks to 9 months
old. The youngest otters (2?5 weeks) arrived during the ?rst few years of the
program. Since 1994, all of the orphaned cubs were estimated to be at least 5 weeks
old. The number of otters arriving each year decreased during the period: 25 otters
arrived during the ?rst 9 years, compared to nine during the second 9 years of the
program. There were 6 years in which no otters arrived (1986, 1990, 1994, 1995,
2000, and 2001).
In the wild, giant otters give birth once a year from early September to mid
October, at the end of the wet season. Most of the otters arrived at Karanambu
between October and January. Details of where the otters were found were often
incomplete, but most came from the North Rupununi area (Massara, Yupukari,
Simuni, Katoka, Rewa, Annai) and were found by local Amerindian villagers,
captured either for trade or pets.
There were four distinct age groups of orphaned giant otters: neonates
(1?3 weeks), cubs (4?10 weeks), juveniles (11?20 weeks), and sub-adults (5?12
months) (Table 2). Age groups were based upon size, estimated age, estimated
or actual weights, dental development, and feeding behavior. Weights were
obtained in some cases by acclimating the otters to being lifted and held by D.
McTurk, standing on a scale. Others would not tolerate this procedure, nor
would they tolerate being placed in a box for weighing. Their weights were estimated
using the known weights of companions or data obtained from other otters of
similar age.
Hand-Rearing and Rehabilitation of Giant Otters 155
Hand-Rearing
Housing.
Housing for new arrivals was identical for all otters: they spent their ?rst few
days in the bathroom of D. McTurk to ensure a regular feeding schedule, and to
begin the process of bonding with a human caretaker. Their transport crate (wooden
box with slats or sky kennel plastic domestic animal crate) served as their ??den?? and
remained with them. On their ?rst day of arrival, the cubs were ?rst placed in a small
plastic tub with water to encourage defecation. Fresh scat, their own or that from
other otters on the premises, was used to mark a suitable ??sprainting?? site and to
Table 1. Orphaned giant otter cubs (Pteronura brasiliensis) hand-reared and rehabilitated at
Karanambu, Guyanaa
Otter no. Year Sex Age Origin Time observed in wild after return Statusb
1 1985 # 2 weeks? Simuni 2 year KP
2 1987 ~ 8 weeks Kotoka 7 year RR
3 ~ 10 weeks Massara 7 year RR
4 1988 ~ 14?16 weeks Simuni 3.5 year RR
5 # 5 weeks Yupukari 1 year RU
6 ~ 5 weeks Yupukari 1 year RU
7 # 2 weeks? Simuni 14 day DC
9 # 8 weeks Yupukari 14 day DC
8 ~ 4 weeks Yupukari 2.5 DP-KP
10 1989 ~ 5?6 weeks Yupukari 2 year RR
11 # 5?6 weeks Yupukari 2.5 month DC
12 1991 # 3 weeks Simuni 4 year RR
13 # 10 weeks Yupukari 4 year RR
14 # 10 weeks Kotoka 4 year RR
15 1992 # 8 weeks Massara 1.5 year DC-KC
16 # 8 weeks Massara 4 year RR
17 ~ 8 weeks Annai 4 year RR
18 # 8 weeks Maraswatta 2.5 year RR
19 # 8?10 weeks Yupukari 2 year RR
20 # 8?10 weeks Massara 2 year RR
21 1993 ~ 3 weeks Massara 3 year KP
22 # 9 weeks Katoka 1 month KO
23 # 9 weeks Katoka 1 month KO
24 ~ 9 weeks Katoka 1 month KO
25 ~ 9 weeks Katoka 3 day DC
26 1996 # 10 weeks Simuni 1 year RU
27 # 10 weeks Simuni 3 month KP
28 # 9 monthnths Quebana 4.5 year KO
29 1997 # 5 weeks Yupukari 1 week DC-KO
30 1998 ~ 9 weeks Yakarinta 8 month DP-KP
31 1999 # 8 weeks Yupukari 4 year RR-DP
32 ~ 8 weeks Yupukari 4 year RR-DP
33 2002 # 12?14 weeks Rewa Alive RR
34 # 8?10 weeks Kurupung 6 month KO
aNo otters were brought to Karanambu in 1986, 1990, 1994, 1995, 2000, 2001.
bKP, killed by people; KO, killed by other giant otters; KC, killed by caiman; RR,
rehabilitated and recorded in wild; RU, rehabilitated and unrecorded in wild; DC, dead as
cubs; DP, presumed dead.
156 McTurk and Spelman
teach the otter the proper location. The cubs soon used this site exclusively. Once the
newly arrived cubs developed a bond with the caretaker, they could be picked up and
handled as needed. This was particularly important in the event of aggression from
another otter.
Giant otter cubs that were very small remained in the bathroom until the small
tub was no longer large enough for swimming. Between 1985?1998, the cubs were
moved from the bathroom to an adjacent enclosed building, the ??giant otter house.??
This building included a cement ?oored sprainting area, a raised brick grooming
area with layers of towels to simulate clay or sandy soil, room for the caretaker to
dry the otter after its swim, a ??den?? fashioned out of a metal drum laid on its side
and covered with heavy towels or curtains, and a much larger tub (7?10 gallons) for
swimming, made from a large truck tire. Simple ?oating toys such as plastic cups or
puppy toys were used for enrichment.
After 1999, older cubs were transferred to a specially built facility, known as
the ??giant otter pens.?? This open-sided building consisted of three adjacent pens,
located near the main ranch house. For construction, the Philadelphia Zoo donated
building materials and Youth Challenge International provided labor. The pens were
covered with a thatched roof, separated by brick walls, and each contained a
medium-sized tub (bathtub), large pool (approximately 100 gallons), metal drum
??dens,?? and a grooming and drying area.
Howdy panels of metal mesh were included between adjoining pens, set within
the dividing walls; these panels permitted otters of varied ages and acquired at
different times, to meet and interact safely. Draped towels were placed over mesh
panels to gradually introduce new arrivals to resident otters. Otter introductions
were made at mealtimes; eventually, compatible otters were housed together.
Feeding.
Twelve young otters required bottle-feeding for 1?5 weeks after arrival. Bottle
feedings were also often given as a ??comfort?? to older cubs to encourage them to
sleep when they ?rst arrived, even if they were old enough to eat ?sh. The amount
and frequency of bottle-feeding was empirical and driven in part by the requirements
of each individual otter. A human baby bottle, with a cross cut to widen the hole in
the nipple, was used routinely. Most otters were fed 0.5?1.0 full bottle of milk (120?
240 ml) three to four times a day. Optimal positioning for bottle feeding was with the
otter sternal, head up, neck extended.
Table 2. Four age groups and estimated weights for young male and female giant otters (34 total),
Pteronura brasiliensis, presented to Karanambu for hand rearing and rehabilitation between 1985
and 2002
Age group Estimated weight
range (kg)
Estimated
age range
Males Females Total (34)
Neonate 0.5?2.0 1?3 week 3 1 4
Cub 2.1?5.4 4?10 week 18 9 27
Juvenile 5.5?12.4 11?20 week 1 1 2
Sub adult 12.5?22.0 5?12 month 1 0 1
Hand-Rearing and Rehabilitation of Giant Otters 157
Of 12 cubs that were bottle fed for several weeks, 10 were given infant human
milk replacer only; two also received a veterinary formula. The composition of the
human milk replacer varied depending upon the availability of this product in
Guyana, but a powder mixed with water was used. The veterinary milk replacer
product (Zoologic Milk Matrix 30/55, PetAg, Inc., Hampshire, IL) became available
initially in 1997 (courtesy of Karl Kranz and the Philadelphia Zoological Society).
The Karanambu Trust subsequently purchased milk formula as needed and shipped
it to Guyana.
Diarrhea developed in three otter cubs fed with human milk formula. The ?rst
otter to develop this problem was the ?rst cub brought to Karanambu. This was a
very young otter (estimated 2?3 weeks) with its eyes barely open; trial and error was
used to develop a feeding strategy. Human powdered milk mixed with water at a
standard dilution was used initially, but the otter developed persistent, severe
diarrhea. The formula was substituted with a mixture of electrolyte solution and
chicken eggs until the otter?s stools improved. The egg was gradually replaced by
milk powder and the concentration was adjusted to a 1:3 dilution. As this cub grew,
it remained very small. It also developed premature dental wear involving its canines,
and was never rehabilitated.
For subsequent cubs, the concentration of the milk formula was increased to
increase the calories provided. Cubs were started on a dilute mixture (1:4) that was
gradually increased, in some cases as high as 1:1 dilution depending on the individual
otter. Milk concentration was adjusted on a daily basis to maintain normal stool
consistency (loose, curd-like, light colored). Stool color darkened gradually as more
?sh was eaten. If diarrhea occurred, otters were given an egg/electrolyte mixture for
several feedings until stools improved, and then transitioned back onto milk
formula. One other otter grew to a relatively small size for an adult, developed
fractured canines, and was never rehabilitated. This was a young male that arrived at
the approximate age of 8?9 months in poor physical condition; its diet as a cub was
unknown.
Young otters learned to suckle from the bottle quickly. They also tended to
hold onto the nipple and attempted to nurse even when the milk was gone, taking in
air and small amounts of ?uid. In 1986, one cub died of presumptive aspiration
pneumonia, which was associated with this behavior and bottle-feeding. With
experience, bottle-feeding techniques were modi?ed so that the bottle was pulled
away from the otter before it was emptied to minimize the risk of aspiration. Giant
otters were not encouraged to drink milk out of a dish because they tended to
submerge their noses, blow bubbles, and sneeze rather than drink.
The cubs were weaned by daily offers of freshly killed ?sh, either in small strips
or small whole ?sh. In the case of very young cubs, ?sh was not offered until after
their eyes were open and teeth were evident. Most cubs started to eat ?sh by 3 months
of age. Species offered were usually red piranha, Serrasaemus nereteri, lukunani (also
known as peacock bass), Cichla ocellaris, and huri, Hoplias malabaricus.
The transition onto ?sh was abrupt in every case. From the ?rst time it tasted
?sh, each otter quickly developed a ravenous appetite. Fish feeding volumes were
increased concomitant with the cub?s appetite, whereas milk volumes were decreased
accordingly. As the cubs matured, they developed a preference for the more bony
species (e.g., red piranha and huri). Dark colored, semi-formed stools with tiny ?sh
bones and scales were considered normal for young giant otters eating ?sh. If ?sh
158 McTurk and Spelman
was scarce (wet season or very beginning of dry season), beef was offered to
orphaned otters. Although the otters would eat the beef and seem satis?ed, they did
not seem to digest it well. Stool quality with this diet was poor, with a strong smell,
and pieces of undigested meat.
Older cubs and juveniles were offered two to four small whole ?sh at each
feeding, three to four times a day. As the otters matured and returned to the river,
they were encouraged to forage on their own. During their return to the river and
transition back to the wild, juveniles and young adults were offered freshly killed ?sh
intermittently (1?2 times/day) as a supplement to their diet.
Swimming, grooming, and sleeping.
The daily routine for all otters, regardless of age, was similar. They were
offered three to ?ve meals per day. After meals, they were given the opportunity to
swim, dry off (with towels), and sleep. Feeding times were usually early morning,
mid-morning, early afternoon (two to three daytime feedings depending on demand)
and late afternoon. Depending on their stage of development, the cubs were carried
or led down to the Karanambu landing to swim. Depending upon water levels, the
river in this area formed a small pond and sand bank. The otters were coaxed into
the river by feeding them pieces of ?sh at the water?s edge. Once the otters were
swimming and foraging for live ?sh on their own, they were given the option to
remain at the river during the day or to return to the pens between feeds.
The swimming and grooming/drying sessions for older otters often lasted an
hour or more and were monitored closely by staff. Typically, once the otters ?nished
swimming, they would seek out a suitable grooming and drying area; these included
the sand banks along the river and the layers of dry towels provided in their pens.
Every evening, Karanambu staff would help dry the otters and groom them quietly
until they fell asleep in their ??dens.??
Each otter was provided with a soft ??chewing cloth?? on which they would suck
or gnaw, engaging in nursing behavior until they fell asleep. This was considered
particularly important as it supplied an alternative outlet for their urge to suckle;
otters housed together otherwise showed a tendency to damage each other?s ear and
tail tips. It was also essential that the cubs? wet towels be replaced with dry bedding,
given the importance to this species of a dry and well-groomed coat, and the fact that
they no longer had access to the body heat of their family group throughout the night.
Survival and health problems.
Twenty-eight of 34 otters (82%) survived to an age and size suitable to start the
process of rehabilitation (Table 1). Six cubs died during hand-rearing. Of these, four
died from illness or injury within days of arrival and before they could be fully
evaluated. Two were killed; one by a caiman and one by another orphaned otter.
Overall, health problems were minor among otter cubs during hand-rearing.
Most new arrivals were thin and judged to be mildly dehydrated, based upon
reduced skin turgor and tacky mucous membranes. Frequent feedings and access to
water, as well as a suitable drying and sleeping areas, corrected these problems
within a few days. Two otters had deep wounds around their neck (from being tied)
such that the top layer of brown fur was not renewed and their pelts remained
scarred by cream-colored fur; others had super?cial abrasions around their necks.
All of these wounds healed. One cub arrived infested with ?eas, and several others
Hand-Rearing and Rehabilitation of Giant Otters 159
with ticks; these infestations were assumed to be the result of their environment after
their capture and before arrival at the ranch.
Two giant otters housed together as cubs (in the 3-pen system) developed
excessive allogrooming behavior that resulted in lacerated tail and ear tips. In this
instance, the behavior abated as the animals grew to young adults (16-week-old male
and a 12-week-old female) but the wounds persisted once they were rehabilitated,
presumably due to interactions with other giant otters (wild and rehabilitated) and
possibly piranhas.
During the early stages of rehabilitation, giant otters often returned to
Karanambu with digit, foot, head, and neck wounds, especially during the wet
season. On occasion, rehabilitated otters returned to Karanambu with ?shing arrows
or hooks embedded in their head, neck, or shoulder area. Severe wounds were
treated accordingly (including removal of arrows or hooks) if the otter could be
coaxed back to the pens, and treatment initiated with antibiotic and anti-
in?ammatory therapy (Table 3).
Anesthesia was required on one occasion in a sub-adult rehabilitated female
requiring surgery with an arrow point embedded in her neck. The otter was given
intramuscular injections by hand of xylazine (estimated dosage ? 2.5 mg/kg) for
sedation, followed by ketamine hydrochloride (estimated dosage ? 2.5 mg/kg) for
anesthesia; after the surgery was completed, the anesthesia was reversed with
yohimbine (estimated dosage ? 0.125 mg/kg).
Because injured rehabilitated otters often returned to the ranch landing at least
once each day to rest, oral antibiotic treatment was possible. The otters would,
however, avoid tablets in ?sh or refuse ?sh containing liquid antibiotics. The most
successful antibiotic over the years was amoxicillin (various manufacturers), given
two or three times a day. Enro?oxacin (Baytril, 60 mg; Bayer Corporation, Shawnee
Mission, KS) was also successful when once a day dosing was required, as in the case
of the female otter that survived surgical removal of an arrow point. Cephalosporin
antibiotics were unpalatable and refused after the ?rst dose. In cases where severe
swelling or cellulitis associated with injuries was present, low dose aspirin therapy
was administered.
Beginning in 1999, giant otter cubs and Karanambu ranch domestic dogs were
dewormed regularly. For the cubs, one of three standard anthelminthics was given
on a rotating basis every 4?8 weeks (various manufacturers): ivermectin paste 2%,
Table 3. Antibiotics and anti-in?ammatory drugs and dosages administered, orally in ?sh for
minor wounds and lacerations to giant otters, Pteronura brasiliensis, during hand rearing and
rehabilitation
Drug Dosage
Typical dose for young
adult (15?22 kg)
Amoxicillin (250 mg
chewable tab or capsule)
15?20 mg/kg two or three times
a day
250 mg
Enro?oxacin
(136 mg tabs)
5?7.5 mg/kg once a day 120 mg
Aspirin
(325 mg)
15 mg/kg once or twice a day 325 mg
160 McTurk and Spelman
pyrantel pamoate paste 18%, and Praziquantel tablets. Dosages were extrapolated
from other otter species (Table 4). The domestic dogs were dewormed twice a year
with ivermectin or pyrantel at the same dosages.
Karanambu ranch dogs were also vaccinated annually with canary-pox
vectored canine distemper vaccine 2 weeks apart, followed by annual boosters
(Purevax Ferret Distemper, Live Canarypox vector; Merial Inc., Athens, GA). The
juvenile male giant otter that became resident at Karanambu and was never
rehabilitated was vaccinated in his third and fourth years at the ranch for canine
distemper, again using the canary pox vectored vaccine.
Rehabilitation
Twenty-eight giant otters survived hand-rearing and began the transition back
to the wild. The hand-raised otters would ?rst spend hours during the day, and then
nights, away from Karanambu and from human care. Eventually, they would spend
days, weeks, and months away from the ranch.
Eighteen otters (53%) survived to make this transition complete, moving
permanently away from the ranch. Although long-term monitoring was not possible,
Karanambu staff observed most of these (15) rehabilitated otters repeatedly, for as
long as 4 years after their return to the river. Ten otters were never successfully
rehabilitated (Table 1). Eight of these were killed, including three by people and ?ve
by other giant otters. Of those killed by other otters, one was the male that remained
at Karanambu for 4 years. The two other otters left the ranch but were never seen
again; these were presumed dead, probably also killed by people.
For the 18 giant otters that did return to the wild, the age at which they left the
ranch was variable, with most leaving after the wet season. Most of the otters spent
o12 months at Karanambu and left at the end of their ?rst wet season (September),
when they were approximately 1 year old. Others spent 2 or more years at
Karanambu.
All 18 otters joined nearby groups of wild giant otters, several found mates,
and most were observed again in the area surrounding Karanambu. The
rehabilitated otters would recognize and approach the people who raised them.
They also often visited Karanambu and interacted with other giant otter cubs in the
Table 4. Anthelminthics and dosages administered orally in ?sh to giant otters, Pteronura
brasiliensis
Drug Dosagea
Typical dose for young
adult (15?22 kg) Indication
Pyrantel pamoate
(paste, 180 mg/ml)
10 mg/kg 1.0 ml (180 mg) Nematodes; routine
Ivermectin
(paste, 20 mg/ml)
0.2 mg/kg 0.2 ml (4.0 mg) All parasites, including
ectoparasites
Praziquantel
(34 mg tablets)
5 mg/kg 3 tabs (102 mg) Cestodes
aPyrantel, Ivermectin, and Praziquantel were given monthly on a rotating basis.
Hand-Rearing and Rehabilitation of Giant Otters 161
process of being-hand raised. The frequency of such sightings varied with the wet
and dry season cycle. Otters were found most often at the end of the dry season
(January to mid-May) when they congregated to ?sh in the main Rupununi River,
Simuni creek, or larger ponds. Karanambu staff and their guests encountered giant
otters on nearly every river visit (average length ? 1?2 hr) during this time of low
water because the daily movements of the otters in and out of ponds became known.
In the wet season (mid-May to August), river sightings of giant otters required
4?10 river visits. Rehabilitated otters and wild otters intermittently visited the
landing during wet season to ?sh sometimes on a daily basis for stretches of 3 or 4
days at a time. If noted by Karanambu staff or guests, the otters were often fed ?sh
to supplement their diet, as ?shing was more dif?cult in the wet season.
Rehabilitated otters occasionally appeared at the landing alone in the wet season
to rest and ?sh away from wild otters.
Beginning in 1999, a mixed group of wild and rehabilitated otters established
their territory along a 3-km stretch of river front that included the Karanambu ranch
landing. The group was initially formed when a wild male otter (a transient) began to
visit the landing at Karanambu regularly in the beginning of the wet season 1999 in
search of a mate. Within a few weeks, the wild male returned with an adult female
and this pair then began to interact with the four orphans that were just beginning
the process of rehabilitation at Karanambu. The wild and orphaned otters would
often go off together to the river during the day, with the orphans returning to
Karanambu for the night. Eventually, several of the hand-reared otters were
rehabilitated and joined this adult pair. When the wild pair gave birth to 5 cubs in
2001, the Karanambu family group numbered 9 otters.
The following year, two rehabilitated otters were driven out of the group. Both
returned to Karanambu at the end of the 2002 wet season, interacting with a new
male orphan being hand raised. The pair of rehabilitated otters then moved on, while
the young male joined the Karanambu pack. As of the 2003 wet season, the
Karanambu pack again numbered seven: the adult pair and their three sub-adult
offspring (two cubs did not survive), one new cub, and one rehabilitated otter.
DISCUSSION
This study is the ?rst to document a long-term rehabilitation program for giant
otters in South America. Along the Rupununi River in Guyana, most (28 of 34) of
the orphaned giant otters brought to Karanambu ranch were hand-reared to the age
and size suitable for return to the river. Over half (18) were successfully rehabilitated
back to the wild. In the only other published account of giant otter rehabilitation,
two young otters were raised and returned to the wild in Columbia [Gomez et al.,
1999].
The overall success of this program is attributed in part to the unique location
of the Karanambu ranch, with access to the Rupununi River that includes prime
giant otter habitat and a relatively low human population. As a result, it was possible
to monitor the young otters closely as they returned to the river, and track their
encounters with wild otters. The dedicated staff of Karanambu was also critical to
the program?s success. Each orphaned giant otter required constant care and
attention for months to years. Once the otters returned to the Rupununi River,
162 McTurk and Spelman
however, it was impossible to track them reliably, particularly during the wet season.
The long-term survival of these rehabilitated otters was unknown.
The location of Karanambu was also a factor in the initiation of the
rehabilitation program. The ?rst otter cubs brought to Karanambu were very young,
several with their eyes just open. These orphans most likely were the result of the
localized pelt trade along the Guyana-Brazil border at that time. Eventually, fewer
neonates and very young cubs arrived each year, presumably because the pelt trade
had all but ceased. However, otter cubs continued to be captured and kept as pets by
Amerindian villagers. Eventually, their captors gave up these otters, presumably
because of their huge appetite for ?sh. Juvenile otters can also be aggressive and
become unmanageable. Because the interest and expertise of the Karanambu staff
was known, these otters were brought to the ranch rather than be abandoned or
killed.
Techniques for hand-rearing and rehabilitating orphaned giant otters cubs at
Karanambu changed gradually over the years, re?ecting successful trial and error.
Published reports were not available for developing protocols for many years.
Recently, protocols have been established for mother reared giant otter cubs in
captivity [Sykes-Gatz, 2001]. In addition, there is one report of the rehabilitation of
two giant otters in Columbia, Central America [Gomez et al., 1999].
Although speci?c data is lacking for giant otters, otter milk is known to be very
high in fat (up to 65%) and relatively high in protein (up to 30%) [Shaul, 1962]. The
availability of milk formula in the interior of Guyana limited nutritional options for
otter cubs and it was impossible to reproduce this ratio using the available supplies.
In addition, even with the development of specialized veterinary milk replacers, such
as Zoologic (30% protein, 55% fat), it was dif?cult to deliver the desired fat content.
This product tends to be thick and lumpy at full strength, and had to be diluted. In
addition, it seems to be less palatable (based upon recent additional experience with
two orphaned otters at Karanambu in 2004) than human milk replacer. Regardless
of the milk formula, young giant otters should be introduced to fresh ?sh as soon as
they express an interest, to ensure optimal nutrition and minimize the risks
associated with bottle-feeding.
All new arrivals learned their new routines quickly, adapting to speci?c
defecating sites in a few days. Most of the giant otters bonded to D. McTurk within 3
days. Over time, it was evident that larger pools were required. In addition, the
opportunity to properly introduce new arrivals to otters already on site was
advantageous.
The giant otter pens constructed in 1999 provided several bene?ts. Although
the giant otters were farther away from the main house, they were able to swim freely
in their pools. The metal mesh howdy panel between adjacent pens also allowed
gradual introductions. Young otters were often found taking a daytime nap on either
side of the mesh, fur to fur, in the shadows of the draped towels. Otter introductions
took place at mealtimes, when each otter was hand fed their share of ?sh. Resident
otters would investigate the new cubs, provoking demonstrations of submission.
When these interactions became too rough, staff separated the otters. Eventually, the
otters refused to be separated and were then housed together.
Introducing the youngest cubs to the river was a gradual process, as many were
fearful of the deep water. Initially, the cubs were led or carried down to the river;
most were at least 12?16 weeks for their ?rst visit. This process was continued for
Hand-Rearing and Rehabilitation of Giant Otters 163
weeks to months until they adapted to this routine on their own. All young giant
otters were resistant, even fearful, of entering the river on their ?rst occasion, some
more so than others. If there was an older and more experienced otter present, the
young ones would follow them and the process went more quickly. When the otters
?nally submerged, they learned to swim and dive quickly. Of interest, all of the otters
exhibited a similar behavior once they learned to swim in the river: they would dive
under water and ingest mud and plant material from the river bottom. This behavior
has also been observed in the wild [Duplaix, 1980].
Teaching young otters, particularly if they were solitary, to ?sh on their own in
the river was also a challenge. For example, the very ?rst orphaned giant otter cub
showed no interest in live ?sh even after it learned to eat ?sh pieces. A number of
strategies were used, including putting small live ?sh in small ponds excavated in
sand banks. The next stage was to release freshly caught ?sh in the river (live ?sh
were not fed in the otter pens to keep the pools clean), and encourage the otter to go
and ?nd them. Subsequently, most of the orphaned otters were fed this way once
they began to swim in the river regularly, and most learned to catch wild ?sh quickly.
Four cubs died early on in the hand-rearing process as a result of injuries or
illness; one of these presumably died of aspiration pneumonia. Aside from these
cases, relatively few health problems occurred in the giant otters reared at
Karanambu. Antibiotic therapy (orally in ?sh) was used effectively for minor and
major injuries. Injured rehabilitated giant otters often returned to the Karanambu
landing to rest and feed. These return visits allowed close examination of wounds
and lacerations, and treatment if needed.
Anesthesia has been rarely reported in giant otters and is challenging given the
size of this species and general tendency for anesthetized otters to show respiratory
depression [Spelman, 1999]. Published reports include ketamine alone (10 mg/kg) or
ketamine (10 mg/kg) and xylazine (1?2 mg/kg), without yohimbine [Marsicano et al.,
1986; Colares and Best, 1991]. Based upon limited experience by the authors with
giant otters at Karanambu and at the Georgetown Zoo, Guyana, the following
protocol was developed: xylazine (2?3 mg/kg) given intramuscularly as a sedative
?rst, followed 10?20 min later by ketamine (2?3 mg/g), and subsequently reversed
with yohimbine (0.125 mg/kg). An alternative was ketamine (5 mg/kg) mixed with
medetomidine (0.050 mg/kg), followed by atipamezole (0.25 mg/kg) for reversal.
Neither xylazine nor medetomidine should be used at these dosages without the
reversal agent on hand. Ketamine (10 mg/kg) combined with midazolam (0.25 mg/
kg) was ineffective in two trials.
Regular deworming for internal parasites was initiated in 1999 as a result of
increased contact between domestic dogs, starting with the resident juvenile male
giant otter (that was never rehabilitated), and two new cubs being hand-reared.
Parasite screening in both otters and dogs showed a mixture of similar cestodes and
nematodes. As a result, routine anthelminthic therapy was given to Karanambu
ranch domestic dogs and the giant otters. This program was continued in subsequent
years: cubs being hand-reared were regularly dewormed to limit potential ill effects
of increase parasite loads while at the ranch.
Also in 1999, vaccination of ranch dogs for canine distemper was initiated to
protect against a potential outbreak that could endanger otter cubs. Only the newly
available recombinant canary pox vaccine from Merial was used for this purpose; the
number of vaccinated ranch dogs varied from one to six (1999?2003). This
164 McTurk and Spelman
vaccination program followed a serosurvey of Karanambu ranch dogs that showed
many dogs with non-protective titers to distemper (RA Weiss, personal commu-
nication).
Domestic animal diseases such as canine distemper and parvovirus have been
identi?ed previously as potential disease risks for wild giant otters in Peru [Schenck
et al., 1997]. The only otter vaccinated for canine distemper was the resident juvenile
male giant otter that remained at Karanambu. Given that this otter showed no
inclination to return to the river, it was considered to be at risk of contracting
distemper in the case that the disease became active in the area. For giant otters
returning to the river system, vaccination was not considered, given the absence of an
active disease outbreak and the impracticality of booster vaccinations.
Among the 10 giant otters that were never rehabilitated, most were known
killed either by people or other otters. Aggression by wild otters led to the death of
?ve otters in three separate incidents. On one occasion, three young cubs were killed
by wild otters in the river, each with a single crushing bite to the skull. One cub was
killed immediately upon arrival by the non-rehabilitated male otter that had made
Karanambu his territory. Inversely, this otter was killed by wild otters that had
accepted two sub-adult otters into their group; the wild otter group turned on the 4-
year-old and killed him as he started to range further, possibly looking for a mate of
his own. This male presumably presented a threat to the wild adult male?s group.
These observations con?rm that giant otters are capable of fatal aggression, similar
to males of other large carnivores (e.g., lions). Although not observed at
Karanambu, cannibalism has also been documented among wild otters in Brazil
[Mourao and Carvalho, 2001].
People killed three (and probably two others for a total of ?ve) orphaned giant
otters during the early stages of their rehabilitation. Two of these were otters that
had developed a taste for poultry (both had received eggs in their milk formula);
people who were attempting to prevent the otters from stealing their chickens killed
them. A third otter, a sub-adult female, was killed after it seriously injured a young
woman.
For the 18 giant otters that were eventually rehabilitated, the process was
gradual. Most otters initially elected to remain at the river after a mid-day feeding
rather than return to the house or pens. They would ?nd an existing den or create
their own natural den in the river banks nearby. Next, they would spend a night or
more on the river, and then return for a feeding or a rest up at the ranch. At this
stage, the giant otters were free to come and go, and were contained at the house or
in the pens only if a con?ict with rival wild otters was anticipated.
Eventually, the juvenile or sub-adult otters began to travel far from
Karanambu, spending days to weeks away from the ranch feeding in the river or
ponds. Often, otters ?rst began to leave the landing and spend time on the river only
after they encountered wild otters. Although these ?rst interactions were not always
positive, they also seemed key to a successful return to the river. Female orphans
generally stayed at Karanambu longer than males, with one exception, and seemed
to attract young males (transients) seeking a mate.
In general, single orphaned otters seemed to have a dif?cult time interacting
with wild otters. Giant otters reared in groups of two or more and rehabilitated at
Karanambu adapted more readily to life on the river. These young otters formed
their own, non-breeding groups. This situation occurred with three different sets of
Hand-Rearing and Rehabilitation of Giant Otters 165
giant otters (different years) over the 18-year period. The 1999?2003 Karanambu
group is the most recent example of successful integration of wild and rehabilitated
giant otters. The movements and social dynamics of this group are currently under
study [Duplaix, 2003]. Of interest, male and female giant otters reared together at
Karanambu were never observed to form breeding pairs, although this remains a
possibility. At least one adult rehabilitated female paired with a wild male and
another rehabilitated female was observed lactating.
Mixed groups of rehabilitated and wild otters would often return to
Karanambu, or to the boats moving through the area, looking for ?sh. In all cases,
the rehabilitated otters, and often the wild otters, recognized the voice and calls of
D. McTurk and swam to the boat or landing to be fed. Because of this, it was
possible to record the movements and behavior of several different otter groups on
the Rupununi River, and to gather detailed information about wild giant otters. For
example, over 3 consecutive years, the otter group that adopted Karanambu as its
territory had two litters. Rehabilitated otters that joined the group were observed
actively participating in cub rearing (moving, feeding, guarding, grooming, playing),
even though they were not related to the juvenile wild otters.
Studies of wild giant otters along the upper Rupununi River have expanded
[Duplaix, 2003]. These include long-term observations of giant otter ecology, social
and feeding behavior, scat sites and scat analysis, causes of cub mortality,
interspecies aggression among family members as well as rival groups, and infectious
disease susceptibility. Studies of giant otters and their interactions with people
include preference for ?sh species and the pattern and frequency of encounters
between otters and local villagers [Shackley, 1996, 1998].
CONCLUSION
The Karanambu giant otter rehabilitation program generated substantial
information on hand-rearing of orphaned otters and returned 18 young otters to the
wild on the Rupununi River. At least one rehabilitated female has reared a litter. At
the same time, the program has served to increase conservation awareness among
local, national and international visitors. Much remains to be learned about this
species in Guyana. Field studies are underway to observe wild and rehabilitated
giant otters in and around Karanambu. Efforts must also be expanded to engage the
local Amerindian community in the protection of the giant otter in the Rupununi
watershed region.
ACKNOWLEDGMENTS
The authors thank Dr. N. Duplaix for her review of this manuscript, the
McTurk family for their support of the Karanambu Trust, and Karanambu Cattle
Company Limited Ranch staff for their hard work and dedication.
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