Behavior Muskellunge are sometimes gregarious, forming small schools in distinct territories. They spawn in mid to late spring, somewhat later than northern pike, over shallow, vegetated areas. A rock or sand bottom is preferred for spawning so the eggs do not sink into the mud and suffocate. The males arrive first and attempt to establish dominance over a territory. Spawning may last from five to 10 days and occurs mainly at night. The eggs are negatively buoyant and slightly adhesive; they adhere to plants and the bottom of the lake. Soon afterward, they are abandoned by the adults. Those embryos which are not eaten by fish, insects, or crayfish hatch within two weeks. The larvae live on yolk until the mouth is fully developed, when they begin to feed on copepods and other zooplankton. They soon begin to prey upon fish. Juveniles generally attain a length of by November of their first year. Predators Adult muskellunge are apex predators where they occur naturally. Only humans and (rarely) large birds of prey such as bald eagles (Haliaeetus leucocephalus) pose a threat to an adult. But juveniles are consumed by other muskies, northern pike, bass, trout, and occasionally birds of prey. The muskellunge's low reproductive rate and slow growth render populations highly vulnerable to overfishing. This has prompted some jurisdictions to institute artificial propagation programs in an attempt to maintain otherwise unsustainably high rates of angling effort and habitat destruction. Subspecies and hybrids Though interbreeding with other pike species can complicate the classification of some individuals, zoologists usually recognize up to three subspecies of muskellunge. The Great Lakes Muskellunge or Spotted Muskellunge (E. m. masquinongy) is the most common variety in the Great Lakes basin and surrounding area. The spots on the body form oblique rows. The Chautauqua Muskellunge or Barred Muskellunge (E. m. ohioensis) is known from the Ohio River system, Chautauqua Lake, Lake Ontario, and the St Lawrence River. The Clear Muskellunge (E. m. immaculatus) is most common in the inland lakes of Wisconsin, Minnesota, northwestern Ontario, and southeastern Manitoba. The tiger muskellunge (E. masquinongy × lucius or E. lucius × masquinongy) is a hybrid of the muskie and northern pike. Hybrids are sterile, although females sometimes unsuccessfully engage in spawning motions. Some hybrids are artificially produced and planted for anglers to catch. Tiger muskies grow faster than pure muskies, but do not attain the ultimate size of their pure