Biology - Aotus

Question 1

What type of monkey are owl monkeys? How much do they weigh?

Answer 1

NWM. Approx. 1 kg

Question 2

What is unique about owl monkeys related to other simians? What do they lack, unlike other nocturnal mammals? What is their proportion of rods and cones.

Answer 2

Only nocturnal simian. Lack tapetum lucidum. Decreased cones, increased rods.

Question 3

What is unique about the metabolic rate of owl monkeys? Why might this be?

Answer 3

Low metabolic rate. Possibly an adaption of nocturnal mammals to allow survival with less energy consumption.

Question 4

Although owl monkey belong to a single genus, they have a wide variation in what?

Answer 4

Diploid chromosome number, from 46-56. Can see variation within same species, but it does not appear to result in speciation or cross-infertility.

Question 5

Owl monkeys can be generally categorized into what two groups?

Answer 5

Red- and gray-necked groups.

Question 6

Where are owl monkeys geographically distributed?

Answer 6

Western Panama to northern Argentina. Gray-necked group north of the Amazon, red-necked group south.

Question 7

Describe phenotypic differences between gray- and red-necked owl monkeys.

Answer 7

Gray: Agouti or gray neck identical to dorsum and torso, intrascapular crest of hair, and elongate pectoral glands with feathering of periglandular hair.
Red: Monochromatic pehlomelanin hairs same color of ventrum, intrascapular whorl, and rounded pectoral glands with surrounding hairs whorled.

Question 8

Describe the social grouping of owl monkeys in the wild.

Answer 8

Monogamous pairs within an extended family with 2-3 offspring, usually an infant, juvenile, and subadult. Subadult leaves family group at 3 years old to establish its own territory. Varies between species what nonbreeding/noncycling sexes are tolerated in the group.

Question 9

How can owl monkeys be sexed?

Answer 9

Lack sexual dimorphism and can be hard to differentiate. Nipple protrusion in females greater than 5 years of age.

Question 10

How does the adult male and offspring participate in infant rearing?

Answer 10

Adult male and offspring actively participate in infant care, male carries infant over 80% of time. Male is fairly certain of paternity and increases future reproduction. Increase survival of offspring and allows increased foraging opportunities of female.

Question 11

When are owl monkeys more active at night?

Answer 11

With moonlight. Travel more and more social on moonlit nights.

Question 12

What species of owl monkey is not strictly nocturnal? Why?

Answer 12

A. azarai. Likely environmental factors.

Question 13

What substances to owl monkeys utilize for scent marking?

Answer 13

Urine and glandular secretions

Question 14

Why do owl monkeys drink their mate’s urine and participate in urine washing?

Answer 14

Likely territorial, not sexual.

Question 15

Where are scent glands found? What is the purpose of scent marking?

Answer 15

Found on face and brow, sternum, and subcaudal gland in perianal region. Role in sexual recognition and intermale aggression, little effect on male sexual behavior.

Question 16

How long is the estrous cycle in owl monkeys? What species is unique?

Answer 16

15-18 days, A. azari have longer cycle at 22 days.

Question 17

Do owl monkeys menstruate?

Answer 17

No

Question 18

When are owl monkeys receptive to a male? Which NWM is this different from?

Answer 18

Throughout ovarian cycle. Differs from squirrel monkeys in which copulation is limited to the day of ovulation.

Question 19

Which two hormones rise after ovulation? When do they peak?

Answer 19

Estrone (peak 5 days) and progesterone (peak 8 days)

Question 20

Describe hormone levels in NWM.

Answer 20

Extremely high peak plasma steroid levels.

Question 21

Describe the testosterone cyclicity in owl monkeys. How does this differ from macaques and lemurs.

Answer 21

Circadian rhythm with highest concentration during day (rest period) and lowest at dark (active period). Daily changes are opposite those of macaques and lemurs, but same in terms of activity cycles.

Question 22

What is the gestation length of owl monkeys?

Answer 22

Varies. 117 - 148/159 days.

Question 23

When is urinary chorionic gonadotropic detectable? What other hormone is detectable? When does it peak?

Answer 23

UCG detectable from 5-6 weeks following conception until 1 week before parturition. Corticotropin-releasing hormone peaks at mid-gestation, at 60-80 days.

Question 24

What is the average interbirth interval? What happens with interbirth interval in multiparous females? How does male behavior impact interbirth interval?

Answer 24

Average 253 days. Declines with increasing births, declines with higher frequency of food sharing from males to females.

Question 25

Do owl monkeys have a postpartum estrus? Seasonality to breeding? How does this differ from squirrel monkeys?

Answer 25

No postpartum estrus. No breeding or birth seasons in captivity, unlike squirrel monkeys.

Question 26

How many offspring do owl monkeys typically have?

Answer 26

Singletons, twinning is rare.

Question 27

What is the preferred resting position of infants?

Answer 27

Ventrolateral 3-4 weeks, dorsal clinging > 4 weeks.

Question 28

When do infants start to get off their parents, eat solid food, and wean?

Answer 28

Get off parents at 3-6 weeks of age, eat solid food at 35-60 days, and wean by 4-5 months.

Question 29

When does puberty occur? What is a useful indicator of pubertal development?

Answer 29

Puberty between 300-400 days in males and females. Indicator of pubertal development is growth of sub-caudal scent marking gland at base of tail, which corresponds to increasing testosterone in male.

Question 30

When are owl monkeys sexually mature? Is there aggression towards pubertal offspring?

Answer 30

18-24 months. No increase in aggression as offspring progress through puberty.