The Sex Lives of Aquatic Mammals

Guess the PUNch line:

Bjorn Friede wanted to be the first zoo keeper to breed porpoises in captivity, but no matter what he did, he could not get the animals to mate.  Finally, he convinced the director of the zoo to allow him to go on a field trip to see if he could find out what would put the porpoises in the mood.

After traveling thousands of miles, Bjorn found a beautiful tropical lagoon where he could sit on the shore and watch the porpoises in their native habitat.  He watched them swim and play and mate, but he came to no conclusion about what triggered the mating behavior.  Then, he suddenly noticed that each porpoise mating was preceded by raucous calling by the mynah birds in the trees over his head.  He observed the scene for a few more days and became convinced:  the bird calls were some sort of aphrodisiac for the porpoises.

Bjorn hurried back to the zoo with a plan to borrow two mynahs from the aviary.  Bjorn was about to make zoological history.
But Al Katraz, custodian of the aviary, wouldn’t agree to lend Bjorn the birds.  He was envious of Bjorn, whose porpoise charges gave shows and attracted so many more visitors than the aviary, to say nothing of Bjorn’s recent jaunt to a tropical paradise at zoo expense.    Katraz was adamant—the mynah birds were too valuable to submit them to the dangers of being moved to the porpoise pool.
Bjorn was determined, in spite of everything, to have his way.  He hatched a daring plan to kidnap the birds in the middle of the night.  The only problem was that Bjorn was sure Al Katraz would be on his guard for just such a scheme.  In fact, he had seen that Al was spending a lot time with Hans Hupp, the head of zoo security.
The shortest way from the aviary to the aquatic mammal pool was through the lion’s den.  Bjorn decided it was the only way.  To make sure he didn’t have any trouble with the cats, he added a strong animal tranquilizer to their food when no one was looking.

That night, he stole into the aviary, took the birds, and tiptoed into the lion’s cage, but he found that two huge sleeping males had lain down right in the doorway.  Frightened but determined, Bjorn crept up to the sleeping lions.  Just as he began to climb over them, bright lights went on all around him.

Hans, Al, and the local sheriff were all there.  Bjorn was arrested and the sheriff charged him with…….
You name the crime!