Setting aside the notion of determining the number of individual animals on the planet for a moment, merely determining the number of species on the Earth is challenging. Science has only been able to offer estimates thus far, and totals vary greatly. Using a new technique based on scaling, ecologist Camilo Mora, a marine ecologist at the University of Hawaii, and his colleagues at Dalhousie University in Halifax, Canada, have estimated the Earth is home to 8.7 billion species. However, this figure is includes plants and fungi, as well as animals, Estimates for the just the animal kingdom vary widely, though the best estimates are on the order of 1 to 2 million species; some sources site an upper bound of 50 million animal species.