Victoria Brokaw
Article Summary
Introduction
Over the last 300 years the numbers of free-living red squirrels (Sciurus vulgaris) has
greatly diminished in United Kingdom. Many believe that low numbers are related to the fact
that red squirrels depend on the availability of the fruits and seeds of the trees in the United
Kingdom (UK). Around the 1800s there was another species of squirrels introduced, the gray
squirrels (Sciurus carolinesis). About 15 to 20 years after the gray squirrels were introduced in
UK, the red squirrels have disappeared from most of the British woods. The disappearance can
be linked to a combination of factors (Garriga et al 2004).
With the competition for the food and space with other species, the red squirrels are at
risk for extinction. Due to poor nutrition and conservation these squirrels are at risk to develop
Metabolic Bone Disease (MBD). The research about the MBD is pretty limited and the disease is
believed to not be considered a threat in the conservation of the red squirrels whether they are
wild-caught of free-living.
The study aim is to provide information on whether the bone density is related to the fact
that red squirrels are competing with the gray squirrels for food and space.
Materials and Methods
The squirrels chosen for the study were taken out of Cumbria (Cu), UK with gray
squirrels present and from the Isle of Wight (IoW), UK where there are no gray squirrels. CU
samples included seven males and three females, IoW samples included four males and six
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females. The bodies were in good condition which meant that the specimens were healthy at
their time of death.
The bones were examined through radiology to see if there is any bone density erosion
present. Only long bones were examined because red squirrels have small skeletons. The bones t
examined included humerus, radius, femur, tibia and ilium (Garriga et al 2004). The bones were
scored for erosion on a scale from 0-2 which meant no, slight, or severe erosion.
Researchers used a high resolution software program to calculate the area where the bone
has been mineralized, and bone mineral density (BMD). Bones were in the water bath between
10-13 minutes depending on the size. The procedure was carried out over two days by the same
researcher in order to get accurate results.
Results
There wasn’t any radiographically detectable erosion that can be seen. There was slight
bone density erosion in five of the squirrels out of twenty. Four of the five were females and one
male. The squirrels taken for IoW were shown to have thinner cortices in tibia and the humerus.
The sample from Cu had higher BMD’s in comparison to IoW in the regions of femur and
humerus. Two of the female squirrel samples one from each region were found to be pregnant at
the time of death. They had the BMD that was in the range that was higher than most other
samples.
Discussion
Bone is constantly changing due to resorption and formation. When it comes to adults,
the bone loss occurs slowly depending on the factors and cause of the loss. Environmental and
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genetics factors play a major role on the growth of the bones depending on the residential area as
well as family history. Sometimes, the squirrels are born with a low bone mass and never
strengthen it as they mature. Low bone density in IoW squirrels suggested osteoporosis that can
be caused by malnutrition, vitamin C deficiency, and estrogen deficiency as well (Garriga et al
2004).
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Bibliography
Rosa M. Garriga et al. (2004). Bone Assessment of Free-Living Red Squirrels from the United
Kingdom. Journal of Wildlife Diseases, 515-522.