Tracking deer births from space

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Researchers were able to track when deer are likely to start giving birth by looking at the health of surrounding vegetation(Credit: US National Park Service)

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NASA's extensive web of satellites has been used for everything from spotting shipwrecks to helping farmers combat draught, but a new project has turned them towards something a little different yet – analyzing deer populations. Making use of the Terra and Aqua probes, the project studied the animals' environment to accurately predict their fawning season.

The easiest way to know when deer will start giving birth is to pay attention to their surroundings. In the late stages of pregnancy, and in the early part of a fawn's life, a doe needs access to plenty of rich vegetation. Birth rates hit a peak just a little before the height of plant growth every year, so gaining a better understanding of exactly when that's occurring can help predict when fawning season is about to begin.

Biologists and land managers already track deer populations, in part so that they can determine how many hunting permits to issue, but the data provided by the new project is far more precise, allowing for close estimations of the start and peak of the season for individual regions.

The project makes use of a system designed to track the health of vegetation, known as the Normalized Difference Vegetation Index (NDVI). The index is designed to measure how plants absorb and reflect back light, with increased levels of reflected infrared light indicating healthier vegetation. On a basic level – the greener the landscape appears, the healthier it is.

The project focused on a large region stretching from southern Idaho to central Arizona, which was split into three separate zones. Using the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites, the researchers measured the NDVI every day for an entire calendar year.

The collected data revealed a lot about the region, showing that greenness peaks later in southern latitudes than in more northern areas – something that the researchers attributed largely to consistent moisture from snowmelt nourishing the roots of mountainous vegetation.

With the southern latitudes relying more on rainfall starting in the late summer, the vegetation becomes healthier, or more green, at a later date. That difference translates directly to dear birthing trends, with does beginning to give birth later in the more southern regions.

The project is a good example of how satellite data can have a significant impact back home. Deer have a significant economic impact in the US, not least thanks to their role in hunting. Tracking their population trends helps us better understand and predict any changes that may occur as regional climates shift or events such as droughts occur.

Full details of the project were published online in the journal PLOS One.

Source: NASA

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