But designers of the 15-year-old Tropical Forest
didn't figure on Little Joe, a 5-foot-tall, 300-pound adolescent
gorilla who, like human teenagers, was increasingly restless with life
at home. Little Joe, 11, was able to scale a steep wall and cross the
moat because he has not yet gained the weight to fill out his long arms
That's when startled zoo volunteers spotted Little Joe
with nothing between him and the public except a potted plant.
Zookeepers quickly evacuated the one family in the Tropical Forest that
morning, allowing Joe to tour the forest exhibit building, returning to
the ape enclosure on his own 10 minutes later.
Though no one was hurt, the incident alarmed zoo staff since there had never been a successful gorilla escape before.
brief brush with freedom in August underscores a growing problem at
American zoos: an increasing number of young male gorillas who are both
agile enough and restless enough to challenge the security systems that
While the growth is only part of an overall 38 percent
increase in the captive gorilla population since the 1980s, zookeepers
say the adolescent males present the most problems.
challenge and a growing challenge in North American [zoos]," said John
Linehan, president and CEO of Zoo New England in Boston, which runs the
Franklin Park Zoo. The zoo has acquired three male gorillas since 1998.
many zoos, including Franklin Park, the gorillas live in a single group
of males and females rather than in gorillas' more natural grouping, a
harem where a single sexually mature male mates with several females.
The young adult males, called bachelors, can start to become a social
problem between the ages of 10 and 19 as they start to become more
interested in the females.
Victor Camp, zoo director at St.
Paul's Como Zoo in Minnesota, compares the adolescent ape problem to
the "bar male syndrome:" The guys in the bar are getting along fine,
playing pool or whatever, until the women arrive and their whole
attitude changes. "They start strutting their stuff," Camp said.
males start to act out, the best solution is to remove them from the
larger group. But, because most zoos do not have multiple long-term
holding areas for gorillas, they have trouble nipping conflicts in the
As a result, bachelors can become restless, and at times,
physical. A young gorilla escaped from the Como Zoo in 1994, leaping
nearly 12 feet onto a boulder and jumping across a moat to climb out.
Another male gorilla, named Hercules, broke loose at the Dallas Zoo in
1998. Hercules bit a zookeeper and then dragged her down a hallway.
are not the only problem. The combination of massive size and an
immature mind can be dangerous. Camp said that while males are not
aggressive by nature, they can unintentionally hurt each other by
posturing, throwing their arms at each other, or accidentally brushing
up against large canine teeth.
For instance, Kitombe, a
17-year-old male at Franklin Park, deeply ripped another gorilla's calf
muscle during a skirmish several years ago.
In a way, the zoos
are victims of their own success: Captive breeding programs have worked
almost too well, boosting the number of captive gorillas in the United
States from 270 to 375 over the last 20 years. But while zoos can
increase the birthrate, they cannot control the gender of baby gorillas.
problem we have in a captive environment is that there are an equal
number of males and females," said Tara Stoinski, manager of
conservation programs for Zoo Atlanta in Georgia.
Species Survival Plan, the group in charge of managing endangered
animal populations in US zoos, does not offer much guidance because
zoologists are just starting to understand captive gorilla behavior.
Atlanta, which just finished a two-year study of adolescent males at
seven institutions, is about to issue a report suggesting that the
bachelors be grouped together, but away from females. "The data
suggests that bachelor groups are good for males," Stoinski said,
keeping them socially engaged without as much sparring.
meantime, zoos employ a number of methods to control problem behavior
and to keep the peace among their gorilla groups. The design of the
enclosures themselves is key in minimizing dangerous encounters.
basic premise is that the animals need to get away from each other,"
Camp said. "You try to create avenues of escape where one [gorilla]
can't be cornered by another."
The Como Zoo built a bridge in its
gorilla enclosure so that animals could run in a circle. If a chase
occurs, they eventually tire out. The Franklin Park Zoo built in
climbable walls to offer escape routes to gorillas trying to avoid
To prevent future escapes, the Boston zoo will also add hot wires to the top of the enclosure.
some cases, zoos may use psychotropic drugs to handle aggressive
behavior. "If the aggression is too severe and is potentially a threat,
the zoo may provide some sort of medication to the animal," Camp said.
"We haven't done that."
Linehan said that the Franklin Park Zoo
experimented with low dosages of antidepressants and anti-anxiety
medications about five years ago. "We didn't see any positive effects
so we discontinued use," he said.
Looking ahead, institutions
building new gorilla exhibits are creating two areas, one for the
family group and one for the bachelor group.
going to need double the number of all-male groups in the future," said
Stoinski, who advocates moving adolescent males into bachelor groups
while they are quite young. "The longer we wait, the harder it's going
to be integrating them."
For the time being Little Joe will
remain with the family group at Franklin Park, but the dynamics are
changing. Little Joe continues to be more aggressive and dominant among
his peers, while Kitombe is ready to breed for the second time and take
on the father role of the group.
Linehan said that the exhibit groups might change or Joe may have to be moved to a new zoo in the future.
group dynamics for the Franklin Park Zoo gorillas have been stable for
five years, Linehan added. "It's been such a joy to watch them grow,
and not worry about the challenges," he said. "Now we will just have to
work through it."
© Copyright 2003 Globe Newspaper Company.