Why are there ticks in southwestern North Dakota?
I grew up in southwestern ND in the 50’s and 60’s. We didn’t have ticks during that time. I am wondering why there are ticks in that area now?
Ramsey County North Dakota
This is a tricky question because there are many factors that influence tick populations. To my knowledge, North Dakota State University and other state agencies have regularly conducted field tick surveys during the past ten years. I don’t know how well southwestern North Dakota has been surveyed and/or if there is enough data to definitively say there were no ticks in this area previously.
There are only a few species of ticks that bite people in the United States, but the most common species in southwestern ND is Dermacentor variabilis or the American dog tick/ wood tick.
Additional species in SW ND that are not as common and do not bite people as often are the Groundhog tick: Ixodes cookie and the Brown dog tick: Rhipicephalus sanguineus.
Many tick species require more than one host to complete their life cycle (see the attached figure) so this is one limiting factor of tick populations. Another factor is relative humidity and temperature. Longer seasons will provide greater chances for ticks to find suitable hosts. Immature ticks are also prone to desiccation, so drier years with less precipitation may not aid their population growth.
Many arthropods are also not regularly distributed, because local conditions may be highly favorable or harmful to specific species. This can result in certain areas with larger populations than others.
Please let me know if you have any questions and if you need me to explain anything in better detail.
Alexander H. Knudson, M.S.