A second genetic problem is the entry of genes from domestic cattle into the bison population, through hybridization.

In 1986, park rangers saw the need to begin controlling the bison population to prevent overgrazing and disease.

Controlling the bison population, however, remains important for Catalina's overall ecological health.

The remnant bison population that escaped the hunt was mostly left alone and it began to increase again.

Presently, the park's bison population is estimated at about 4,000.

Disease, including various viruses, parasites and brucellosis have a greater effect on bison population.

The bison population recovered in a couple of years; Montana's public image did not.

Before the European settlers arrived on the prairies in large numbers the bison population was estimated at about 50 to 60 million.

The bison population established in the 1930s, died out in 1945.

When the army left the park in 1918, the bison population was estimated to have increased to 400 individuals.