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The goal of this study is to determine how many newborn vicuna survive to their first birthday. This will describe mortality patterns of newborn vicuna during the first year of life.
The researchers are trying to find out information about puma predation of newborn vicuna. No other studies like this have been done in San Guillermo National Park. Because of this, the researchers did not make a hypothesis because they are trying to describe mortality patterns without making any comparison to other groups of newborn vicunas.
What percentage of newborns survived to their first birthday? What percentage died before their first birthday?
Twenty (20) newborns were captured and fitted with radio transmitters. Eleven (11) of the newborns survived while nine (9) died. Fifty-five percent (55%) of the newborns survived and 45% died.
What percentage of the newborns were killed by pumas?
Of the nine newborns that did not survive to their first birthday, seven were killed by pumas. 77.8% of the newborn vicunas were killed by pumas. (7/9*100=77.8)
This result could be interpreted as pumas having a high impact on newborn mortality: pumas are the main newborn mortality factor. In other words, pumas have an enormous influence on the survival of baby vicunas.
What percentage of the newborns who died were males? What percentage were females?
Of the nine vicunas that died in their first year, five were females and four were males. Females make of 55.5% of the recorded deaths and males make up 44.5%
What was the average birth weight of the newborns that survived?
There were birth weights recorded for nine of the newborns that survived. Their average birth weight was weight 5,933 grams.
What was the average birth weight of those newborns that died?
The average birth weight of the nine newborns that died was 5,244 grams.
What was the sample size used to estimate each average?
Note that two females have missing birth weights; missing data are common in field ecology and result from different causes. In this case, researchers were attacked by the mothers while handling the newborns. Consequently, they only had enough time to attached the radio transmitter and free the newborn.
Individuals with missing data for a variable (in this case weight) are ignored when estimating the average for that variable. This is why sample size for females is 9 instead of 11.
These conclusions can be drawn from an analysis of the data.
- The results showed that on average surviving newborns were larger than non-surviving ones.
- The survival data suggested that females were less prone to survive to their first year than males.
- The leading cause of newborn mortality was predation by pumas. This was followed by starvation.