In the given graph, the four lines have been drawn. The yellow area shows the four sided habitat. The coordinates of the four corners are (1,7), (2,7), (2,0) and (-7,-9).

From the area of the rectangle, subtract the areas of the two right triangles to find the remaining area of the quadrilateral.  These areas can be found by counting units.

Rectangle:  9 by 16 units = area of 144 sq. units
Right triangle upper left:  bases are 8 by 16 units = area of 64 sq. units.
Right triangle lower right:  bases are 9 by 9 units = area of 40.5 sq. units.