What subtle morphological difference is noted regarding the nasal area between the Northern and Southern Leopard Frogs?

Answer

The Southern species often has a dark triangular patch between the eye and nostril

The text notes that the Northern Leopard Frog typically has a lighter color between the eye and nostril, whereas the Southern Leopard Frog often exhibits a dark triangular patch in this region.

What subtle morphological difference is noted regarding the nasal area between the Northern and Southern Leopard Frogs?
animalclassificationamphibianfrogleopard