Vertebrate Pest Conference Proceedings collection


Date of this Version

March 1986


The M-44 sodium cyanide (NaCN) ejector is an important tool for coyote damage control. For greatest effectiveness, the ejected NaCN mixture must be a dry powder. NaCN readily absorbs and reacts with moisture to cause solidification or "caking" in M-44 capsules. Because it is difficult to seal the capsules water tight, caking has been a chronic problem ever since NaCN ejectors were introduced over 40 years ago. The toxicity and caking properties of three alternate compounds are reported in this paper.

Comparative toxicity tests were made with M-44 ejectors containing NaCN, potassium cyanide (KCN), calcium cyanide (CaCN), and methomyl. Five to eight pen tests on coyotes or dogs were conducted with each compound. NaCN was tested on both coyotes and dogs. Except for one coyote that survived a dose of CaCN, each test animal died after pulling an M-44 and receiving a full charge of ejected toxicant. Average lapsed times from pull to first observed symptoms were 31 seconds for NaCN, 34 seconds for KCN, 63 seconds for CaCN, and 2 minutes for methomyl.

Both NaCN and methomyl were lethal in all pen tests, yet coyote recovery rates (carcasses found/ coyote pulls) in the field were 80% for NaCN and only 24% for methomyl. This difference was attributed to the faster action of NaCN. KCN and CaCN were not field-tested, but results from captive coyotes indicate that KCN would be about as effective as NaCN and CaCN would be less effective. None of the three alternate compounds offers enough advantage over NaCN to warrant the expense of registration, since NaCN is already registered.