CONTINUING EDUCATION
Special Topic: Extern Mary Catherine
Moving the Spider Monkeys – The Saga Continues
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Carlos and Montana in their
Current Enclosure |
This month we eagerly anticipated the big move for Carlos and Montana to their new home. We set up a catch cage in their enclosure and successfully trained them to enter the cage for treats. They were very wary of the cage in the beginning and were extremely hesitant to even approach it. However, Montana first started entering the cage and quickly became comfortable bringing his whole body in and sitting calmly in it as he received grapes (though he often left his tail outside). Meanwhile Carlos was much more nervous and would at first only reach into the cage for treats, never bringing his whole body in and always keeping a grip on something outside of the door with his tail.
We brainstormed on how we could encourage Carlos and Montana to enter the cage entirely AND bring their tails in so that the door could be closed. The solution was simple: we began holding the grape rewards farther back from the cage so that they were unable to reach it with their hands but had to use their tails to grab them. Montana picked up this behavior quickly as he tends to use his tail more than Carlos for retrieving things just out of reach. A day or two passed with Montana getting all the grapes as Carlos looked on unwilling to release his tail from gripping the bars outside of the carrier cage. However, unable to stand by while his brother got all the grapes, Carlos, in a moment of courage and bravery entered the cage and brought his tail in with him to reach for the grapes. Immediately I showered him with praise and grapes the second his tail entered the carrier cage. Carlos experienced an “A-ha!” moment and realized the secret to getting the grapes was to enter the carrier and bring in his tail. He calmed down remarkably once he discovered entering the carrier was not so scary, in fact it was fun and delicious!
A week went by with the boys consistently and eagerly entering the carrier cage and sitting calmly while they received a steady stream of grapes. We decided they were ready to be closed into the carrier and moved to their new home. However, we underestimated the difficulty of this task. Our first few attempts were met with technical difficulties with the closing mechanism of the carrier door. It didn’t take long for Carlos and Montana to get wise to our intentions and, after tolerating our missteps on several occasions; they finally grew suspicious of the cage and our actions and once again refused to enter the carrier at all.
We were all let down by this set back both because we were eager to see them in their new spacious home, but also because we had made such progress in gaining their trust and cooperation. This has been very disappointing, but we have a new strategy and are armed with patience. The regression was to be expected, so we move forward by beginning the process again. By taking small steps, and rewarding each positive behavior, we are already back to having Montana enter the carrier (with his tail inside) to receive rewards. Carlos is more hesitant, so we are continuing to be patient and supportive with him, encouraging any attempt he makes to reach into or enter the carrier cage. In time, we are confident that we will regain their trust and voluntary cooperation. This is vital to maintaining a positive relationship with them and is enormously more humane than resorting to force or frightening them into compliance. Our method of positive reinforcement may take a bit longer, but the lasting benefits of mutual respect between human caregiver and monkey makes all the difference in their quality of life. They deserve nothing less.
Special Topic: Intern Simon
Marmosets and Tamarins, Chapter 10: From dependence to sexual maturity: the behavioural ontogeny of Callitrichidae; by Maria Emilia Yamamoto
Introduction
Ontogeny is a fancy word for the various stages of an organism’s development. In the case of marmosets and tamarins there are four developmental stages: the infant stage, the juvenile stage (also called the adolescent stage), the sub-adult stage, and the adult stage. Each of these phases redefines the role of the individual and is critical to their success.
The Infant Stage
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White-tufted Eared Marmoset Parent
carrying Infants |
The infant stage usually takes place from birth until about nine months of age. It should come as no surprise that this is arguably the most crucial phase in an animal’s development. Just like human infants, tamarin and marmoset infancy is a period of constant learning, socialization, and discovery. Mother’s typically give birth to twins. For White-tufted Eared Marmosets, each newborn weighs between 22-38 grams, and for Cotton-top Tamarins 34-38 grams. Within a matter of seconds after birth, infants are able to grab their mother’s fur, and within minutes they can breast feed. Unhealthy infants receive no special attention, and if they cannot cling on to their parent’s back or vocalize they will be neglected or abandoned by their mother, usually to the point of death.
For healthy infants, within days family members other than the mother will become the newborn’s carriers. For at least three weeks the baby will be carried at all times. By the fourth week the infant has become interested in their physical environment and occasionally begins to leave their caregiver’s back to explore their immediate surroundings. As the weeks go by, they spend less and less time being carried, and more and more time socializing. In weeks 8-12 it is rare to see an infant being carried at all. In weeks 9-13 they are weaned, and it is during this time that they might develop agonistic behaviors (survivalist behaviors which include aggression, defense and avoidance), and will often begin scent-marking as well. By the end of the infancy period, infants have become skilled groomers, and are virtually independent.
The Juvenile Stage
The juvenile stage begins sometime between 4-7 months after birth. At this stage the young monkey is only about ¾ the weight of an adult. During this juncture the tendency to interact with group members other than parents is emphasized. The juvenile marmoset or tamarin can now solicit a grooming session at will. Also, social play becomes more aggressive and roughhousing occurs. Twin fights are not unusual during this phase, and the outcome of these twin fights can often have repercussions that persist into adulthood. In fact, it is believed that this early sibling rivalry is an adaptive mechanism: the siblings can fight it out and establish which is the dominant one during this adolescent stage without causing serious injury to each other, because during this stage they are lacking the longer, sharper teeth of an adult.
Another noteworthy change occurs during this juvenile stage. About five months after birth, juveniles usually get new infant siblings. The adolescents typically are interested in these new arrivals, grooming them, engaging in play with them, and sometimes even carrying them. In the latter part of this juvenile stage patterns of sexual curiosity begin, and juveniles will sometimes mount their younger siblings, or perform genital investigations on them.
The Sub-adult Stage
The sub-adult stage begins between 9-14 months of age. At this stage the monkey is about 82% the weight of an adult. The sub-adult marmoset or tamarin has mastered most of the adult behavioral repertoire (for example: grooming, vocalizing, performing threats, etc.). During this period the monkey reaches puberty, but cannot conceive. Scent-marking is now commonplace, as are agonistic behaviors such as tuft-flicking and pilo-erection (a term used to describe when the fur stands up in agitation, just like cats do). In the case of newborn siblings, sub-adults will play a much more active role in their care giving than they did as juveniles.
The Adult Stage
The adult stage starts between 12-22 months. It is achieved once adult size and appearance is attained. At this point sexual maturity is reached and the monkey is now capable of reproduction. However, as long as an adult remains in their original family group, they will show no changes in behavior. It is not until they are paired that they exercise their ability to reproduce.
Conclusion
Tamarins and marmosets, like humans, undergo the biological changes and learn the social behaviors critical to their success during the various stages of their development. A misstep in any one of these stages could result in an abnormal monkey. Monkey pets never get the opportunity to be properly conditioned as monkeys, and often live in a perpetual state of confusion as a result.
-Rylands, A.B. Marmosets and Tamarins. Systematics, Behavior, and Ecology. Oxford, U.K.: Oxford University Press, 1993.
Special Topic: Intern Olivia
The Complete Capuchin: The biology of the genus Cebus
Chapter Four: Life History and Demography
Capuchins are relatively long lived for primates, living to age 55, and have large brains compared to other monkeys with similar body sizes. The composition of Capuchin groups is multi-male/multi-female. The males leave their home when they reach sexual maturity to join another group and will leave that group after a few years. Females typically give birth every two years after reaching sexual maturity, and this is normally in the dry season or the early wet season.
There are generally three males born for every female. By adulthood this ratio skews in favor of the female with a ratio of three females for two males. Data from the Santa Rosa site between 1986 and 2001 shows high infant mortality. About a quarter of the infants born die before six months, and only 68% survive their first year. Only 39% of Capuchins born make it to their fifth year.
Females begin giving birth around age 6-7 and will continue to give birth every two years. Infants are born every month of the year, but the greatest number of births occurring in January, the second month of the dry season. Conception tends to correlate with an abundance of food, during the rainy months.
Males leave their natal group (the group where they were born) at age 5 and will continue to leave groups every four years or so. Many males will disperse at the same time, and are often related. This normally occurs when there is a meeting with another group of Capuchins and they will break away from their group to join the other. Subgroups dispersing is called fission, and when small groups join together this is fusion. Males leave the groups to prevent mating with their daughters.
“Life on this planet can stand no more plundering. Quite apart from obedience to the universal moral imperative of saving the Creation, based upon religion and science alike, conserving biodiversity is the best economic deal humanity has ever had placed before it since the invention of agriculture.” — E.O Wilson
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