The interactions between mothers and their offspring are vital for successful child-rearing. Due to the energy-intensive nature of reproducing and child-rearing, a mother Alouatta palliata, or mantled howler monkey, will protect the health and safety of her offspring. However, within three years, the offspring must obtain the skills to survive independently. Female A. palliata experiences a gestational period of approximately 180 days. Every two years, females give birth to one child. An infant A. palliata will nurse for the first 18 months of its life. I hypothesize that mothers will maintain closer proximity to infants than to juveniles. My research will be conducted in May 2022 at the La Selva Research Station in Costa Rica's north-eastern rainforests. The primary and secondary forests there create an ideal habitat for A. palliata. The adult A. palliata are primates weighing 4 to 5 kg and covered in black fur. Infants will be covered in gold or silver fur until their fur darkens when they reach sexual maturity at three years old. Data will be collected using instantaneous focal sampling in 10-second intervals that will alternate between mothers and offspring. I will distinguish between infant A. palliata, as those clinging to their mothers, and juveniles as those who nurse but transport themselves predominantly independently. A. palliata mothers will be distinguished by the act of nursing their offspring. I will study the methods applied by the mother, A. palliata, in the rearing of her offspring. I will record their proximity to one another and to others, distinguishing between physical contact, within 1 meter, 3 meters, or a distance greater than 3 meters. I will record their behaviors such as feeding, resting, traveling, and grooming. This data will be compared to data collected on other Alouatta species.
Adults and infants have different dietary intake needs, from how much they eat to the different types of foods they eat. Infants and juveniles need more food (energy) than adults because they are growing. While infants and juveniles need more energy, they are also less proficient at foraging than adults. This, coupled with their higher energy needs, suggests that infants and juveniles will need to spend more time foraging. Prior research on Alouatta caraya reported that as they become older, the amount of time they feed and move decreases. Alouatta palliata also known as howler monkeys, are primarily folivores. They eat a wide variety of different plant species and parts, including, leaves, berries, fruits, seeds, nuts, and flowers. A. palliata infants suckle for 6 months to 1 year on average and then begin to transition to solid foods. It is unknown whether this pattern of infants and juveniles spending more time feeding is true for A. palliata at La Selva Research Station. I predict that A. palliatainfants will spend more time eating than adults. This research will be conducted at La Selva Research Station from May to June of 2022. La Selva Research Station is in Costa Rica, and it is 1,600 hectares of well-preserved old-growth and recovering wet lowland tropical forest. The primary forest takes up 53% of the forest, and the rest is in various types of secondary forest and abandoned land. A. palliata are stoutly built bearded monkeys with a hunched appearance and thickly furred prehensile tails that are naked on the underside of the tip to afford a better grip. The hair is long and thick and is typically black, brown, or red. Data will be collected using 30-second instantaneous scan sampling. I will record the age (infant and adult) and feeding, travel, and rest. I will compare the proportion of feeding scans between infants and adults.
Being the largest New World monkeys, mantled howler monkeys (Alouatta palliata) and spider monkeys (Ateles geoffroyi) vary greatly in terms of appearance, diet, and time budgets. Recent studies show that Alouatta palliata spends about 17% of their time foraging and about 80% of their time in a resting activity. Conversely, Ateles geoffroyi have been shown to budget their time as such: 33.5% foraging, 24.1% resting, 32.6% travelling, and the rest of the time is divided between other categories. This difference in time budgeting is attributed to the difference in diets between species, as Alouatta palliata has a folivorous diet and Ateles geoffroyi has a frugivorous diet. Because fruits are not located in any specific area, but are spread out throughout the forest, there is a general trend of frugivores spending more time looking for food, while folivores spend more time resting to digest food. When comparing similarities between species, simultaneous study of activity budgets between co-existing species is rare. Additionally, activity budgets of Alouatta palliata and Ateles geoffroyi at the La Selva Research Station are unknown. The question then becomes: do these different species attribute their time at the La Selva Research Station similarly? I hypothesize that Alouatta palliata will have more resting and foraging periods compared to Ateles geoffroyi. I will be going to the La Selva Research Station, located in Costa Rica, in May 2022. The La Selva Research Station offers 1,600 hectares of forest where a number of Alouatta palliata and Ateles geoffroyi can be found. Alouatta palliata have fur that ranges from walnut, gold, chocolate brown, and black colors across their bodies; whereas Ateles geoffroyi are reddish brown, yellowish brown, black, or silvery-gray. Weight differences of Alouatta palliata and Ateles geoffroyi are important, too. Alouatta palliata males weigh between 4.5 kg and 9 kg with females weighing 3.1 kg to 7.6 kg. Ateles geoffroyi males, on the other hand, weigh between 7.4 kg and 9 kg, and females weigh between 6 kg and 9.4 kg. Instantaneous focal sampling will be completed at 1-minute intervals. Key characteristics that are going to be observed are feeding, aggression, vocal calling, resting, and travel. This allows a broad enough spectrum that multiple data points are going to be collected for a quantitative analysis. This is completed by comparing the proportion of budget categories observed, by species, relative to the number of scans obtained. These budgeting categories will then be compared to those from other sites.