38960 (Mammals), страница 5

The birth watch involved round-the-clock observations at 15-minute intervals during successive, 4-hour shifts. Observations were recorded by keepers, technicians, and trained volunteers. As soon as any signs of straining or birth fluids were noted, continuous notes were kept and each subsequent contraction or birth-related event was timed and recorded. Behavioral indications of impending labor included restlessness and manual exploration of the vaginal area. Although these signs eventually proved reliable, we used the first, clear contraction as the starting point for measuring the duration of labor. (In human terms, this is equivalent to second-stage labor. The usual criterion of first-stage labor, cervical dilatation, cannot be observed in the wild primate unless restraint is used.) During actual labor, several straining postures were noted; most common were variations of squatting postures and arched-back stretches.

The first birth was to an experienced mother (this was her third delivery) and was documented on videotape. After nearly 8 full hours of labor and 188 contractions, the dam gave birth to a healthy, female infant. These initial observations led us to believe that a labor of this duration was not a basis for concern; however, we soon learned that this was far beyond the average labor length and number of contractions common for this species.

Over an 8-year period, we were able to collect data on 18 births from 8 different mothers in our colony. Our program has provided some valuable information about species-typical birth patterns that we can now use to direct management decisions. We found that the average length of labor to expulsion of the fetus was about 2 hours and 15 minutes, and the shortest labor was only 50 minutes total. The female that required eight hours to deliver in the first case observed then delivered her subsequent infant in only a little over an hour! Although our sample is still small, it would appear that, on the average, first-time mothers have longer and more difficult labors.

Our study determined that the average number of contractions to delivery for lion-tails was 54. The female with the longest labor also had the largest number of contractions (454). In her next delivery, the infant arrived after only 14 contractions, the lowest number recorded during the entire birth study. Based on the average number of contractions seen in 17 successful deliveries, and one ending in stillbirth, contraction frequencies approaching 75 to 100 in number may serve as a warning that intervention will be necessary.

The average length of gestation for 14 pregnancies in our colony was 169.5 days, with a range of 163 to 176 days. This is very similar to what has been reported for other macaques. Our observers quickly discovered that those who watched during the 7 to 11 P.M. shifts were the most successful at being present when births occurred: labor began between the hours of 7:15 P.M. and 3:15 A.M. in every case but one. The exception was one first-time mother that began straining in the early afternoon. This female had a difficult labor, and a dead fetus was later removed by cesarean section after 8 hours of straining and 193 contractions. All the other births resulted in live offspring and occurred between the hours of 8:05 P.M. and 6:28 A.M. Based on previous primate birth records, daytime births are not the norm and may indicate an increased risk to both fetus and dam.

Expulsion of the placenta always took place within about 20 minutes after parturition, and usually it was immediately consumed by the mother. In a few cases, first-time mothers carried the placenta around for several hours, along with the infant, until it could be removed by keepers. Whenever possible, a sample of the placenta is saved for analysis by Zoo pathologists, who check it for abnormalities. After delivery, the mothers carefully lick the birth fluids off their infants, and the neonates begin nursing within a few hours. Each and every female in the study provided excellent maternal care immediately following parturition.

The lion-tailed macaque breeding colonies are now located in the Sun Bear Forest exhibit at the Zoo (one adult male and six females) and in a large, off-exhibit kraal at the Wild Animal Park (one adult male, two juvenile males, one infant male, and ten females). Together these represent the largest captive group of lion-tailed macaques in the world -- about 20 percent of the total captive population. Eight years of patient monitoring, birth watches, record keeping, and evaluation have brought us a long way in the breeding and captive management of this macaque species.

ZOONOOZ, May, 1990 "Nighttime Is the Norm: Labor and Birth in the Lion-tailed Macaque," by Helena Fitch-Snyder, Animal Behavior Specialist/CRES and Donald Lindburg, Ph.D. Behaviorist/CRES.

MORE ON IGUANAS

The environment in which a lizard lives may determine how easily its scent marks can be located by other lizards. Both desert iguanas (Dipsosaurus dorsalis )and green iguanas (Iguana iguana) possess femoral glands on the underside of the hind legs. They use pheromone secretions from these glands to mark their territories. Desert iguanas live in extremely hot and arid habitats, whereas green iguanas live in humid tropical forests. Because these two species of lizards live under such different environmental conditions, it is not surprising that the way their pheromone signals are transmitted differs.

Desert iguanas have scent marks that are nonvolatile, which means that they evaporate very slowly into the atmosphere. These marks are also extremely resistant to chemical breakdown at high temperatures. The low volatility and thermal stability of desert iguana scent marks ensures that they persist under harsh desert conditions, a necessary quality if they are to be used effectively for territory marking. Although these characteristics make scent marks more durable in desert environments, they pose a problem for desert iguanas attempting to detect them if the marks are not volatile; they may be difficult or impossible to locate using smell. Desert iguanas avoid this problem by combining a unique type of visual signal with their scent marks.

One striking property of desert iguana scent marks is that they strongly absorb ultraviolet light. Although these wavelengths are invisible to human eyes, they appear dark to animals able to see ultraviolet light -- much as ultraviolet-absorbing honey guides on flowers look black when UV-sensitive camera film is used to view them. Recent studies have shown that desert iguanas are able to see long-wave ultraviolet light, and they may use this adaptation to detect scent marks from a distance. After scent marks are localized using visual cues, desert iguanas can approach and investigate them in more detail through tongue-flicking. Although it is not known to occur in mammals, visual sensitivity to ultraviolet light has been shown in certain insects, spiders, fish, frogs, and birds. The ability of desert iguanas to detect ultraviolet light may help them solve some of the problems associated with finding scent marks in a desert environment.

In contrast to those of desert iguanas, the scent marks of green iguanas contain a variety of volatile chemical compounds, and they do not absorb ultraviolet light. Behavioral studies indicate that green iguanas, unlike desert iguanas, can detect these scent marks by smell alone. Because the chemical components of green iguana scent marks remain active and transmit well under the humid conditions of tropical forests, green iguanas do not appear to need a visual cue in order to locate scent marks. Research on both iguana species demonstrates how the environment in which animals live can influence the nature of the communication signals they employ.