I've noticed that our rat population has taken a big hit . Last year we had a real good population here in South Dakota. Has anyone else noticed the same?

Whenever it gets dry the rat numbers fall off and I don't mean by a little bit around here, probably true any where. We talk about predators, chemicals, over trapping etc. etc. but there is nothing that hurts rats more than little to no water. The real negative thing is once populations get low then all the fore mentioned factors play a bigger role and many places may stay low for some time unless there are small pockets of rats close by to restock.
We were dry here in April, May and June, looked like a real down turn, has been quite a bit more wet the last couple months, so rat numbers will be OK but less then last year.
Bryce

Hey Bryce...I've often heard muskrats can rebound quickly in good habitat. If the gestation is 28 days... How long before a second litter. My marsh was dry early, but has great vegetation now

Very dry here as well. Little spots have dried up. Hopefully, some of the larger sloughs will hold enough to have a few rats. Not too optimistic about the spring season. X2 on the water. That seems to be the major factor here in SD.

Yep pot holes dried up in many places here it’s common to go through those cycles we get water we have rats it dries up for a few years they are gone.

Yes you can get a litter in a month but if you were dry spring and early summer you missed the first 2 repro cycles and there will not be any litters from the early YOY rats as they are not there. Also if that dry your base number is probably very low as well, so sure you can get rats but at what percent of say a normal non drought year?

I have 3 small sloughs that I trap when there is water in them. Five years ago they were all dry and there were zero rats in 2 and I caught 6 in the bigger one. We had 3 very wet years. Last year those 3 little slough I caught 69 rats in or 10 fold of the poor year, two years ago I got 49 in those 3 areas.

Bryce

If you want to learn more about your prey (which never hurt me) read Paul Errington's "Muskrats and the Marsh" . Required reading for Fish & Wildlife students and has good info on 'rat responses to their environment. Here are some of my observations from our locality on the Great Plains. We all know about 'rat breeding in the spring and float trapping. Momma comes into estrus in late February - early March, gets bred and has her litter in early April. Another 30 days or so and the young are on their own, approx. mid May. Mom must now replace all that energy she expended and if adequate water, food conditions exist, she will be ready to come back in estrus in June - July. IF YOU HAVE POOR WATER CONDITIONS (a dry June - July) she will be more akin to saving her rear than producing a litter so estrus maybe delayed or even skipped. Now you are into August and water might still be in short supply so you better kiss that 2nd litter Goodbye when September shows up. That July - August estrus and litter born in September would have been the kits/smalls/mediums you catch in early November. So the bottom line for me is if you have adequate, stable water in July - you have a 2nd crop of 'rats. Without it, too much stress for survival for them to do much reproducing. "OK Mike so you may have seen all this so tell me something I can use." .... Alright, alright...... When we have years like this and you want to harvest some muskrats, my tip (for here and anywhere you have them) is to concentrate rat harvest on beaver colonies on creeks where they have provided a steady water level most of the summer. After the fall equinox, the beaver will be tending their dams in a big time way. Any rats moving on the creek will not go far from these areas as the increasing water will provide all the food and cover they are seeking in a drought. Some rats will have produced a second litter behind these dams too. Many years ago I watched a mink work over the rats behind a beaver dam for about 25 days. My best count was he took 15 rats during that time period. It was an education watching him. I've had lots of good rat catches behind beaver dams through some pretty dry years and by best day's catch was from 1 farm pond and several beaver dams in a drought year......hope this puts some light on the subject............. the mike

When I was majoring in Wildlife Ecology at UW in the 60's Errington's work on rats was the "Bible" for rat information and it may still be some of the most comprehensive rat research and study yet today. We have had some state agencies doing rat research as of late with the downturn that many have had. If there would have been one researcher with Errington's commitment and working in multiple areas we may have more solid information regarding the fate of muskrats here east of the Mississippi.

Bryce

Amen Bryce, when I graduated from MSU in '80 I went to WI to look at a job on a fish/muskrat farm. Turned it down but the owner had just lost his hired man and was desperate to hire a person. Those two old guys raised and sold fry and fingerlings in the summer and had a registered fur farm that they caught 2500-3000 rats on in the winter. Talk about management!!!!! They KNEW the marsh (which is different than a USDA Wetland) for you Ag guys. LOL..................... the mike

Lots of great information gentlemen.

What stimulates estrus?

Kind of an obvious solution, around here find an active beaver dammed area and you’ll find muskrats.

They did a study a few years back here in Pa. Lots of possible causes for the decline but no solid anwers. Most places I trap have stable water levels and the same cover as they did 30 years ago. What we do have is alt more hawks,mink, and blue heron. I don"t bleive it is pesticides as I assume our farmers here use the same stuff as out west.I don"t know the answer, but I sure do miss rat trapping.

The weird thing is how the rats disappear and seem to be gone and I’m saying gone! The last time things dried up I checked a spring pond out I figured was a good seed spot always has water, full of cattails and it never freezes so the ideal spot during hard times I figured. I was trapping yotes one year close by and checked out how many houses might be there. Not a house to be found I was shocked I did not expect that because everything needed was in that location?

Drought and low stagnant water equals disease carrying source and with tuleremia = extensive muskrat die offs with a slow come back.

High water can deplete the the population also.2018 and 2019 we saw the lowest rat populations ever 2020 was better but still not good.

Errington's disease, tularemia and probably a host of other diseases are relentless in high population areas. Its like the lemmings over the cliff but with bacteria, and probably some viruses as the culprits. Rabbits, hares, prairie dogs etc., all have a population mechanism that is outside simple 1+1 biology. Cycles in these type of mammals are also linked to immigration (into) and emigration (out from) areas or "seed" as fur harvesters refer to a beginning population #. The intrinsic rate of animal population increase is used to estimate the potential growth of #'s over time. In other words.......... In excellent habitat areas, we need some rats to exist or come from somewhere to utilize their maximum reproductive potential to produce a "crop". On the prairie here a drought sends them "out" looking for a place of water and they become "food" for every land/avian predator that could not access them in the water. ............ Now suppose the rain/moisture comes and fills the area with water levels conducive to excellent growth and expansion. ..... But in the prairie pothole and lake regions, recruitment is slow due to distances for a small furry mammal to travel and by the time they follow the yellow brick road (probably their great grand kids) and get to OZ (LOL) 2-3-4 years later, water levels are not optimum. OK now just the opposite.................... Water levels are at maximum levels (on a consistent weekly-monthly-yearly basis) for a huge "crop" and the "seed" exists in place,,,, Wow,,,, we have rats everywhere, overlapping each other's living space and whoops,,,,, pathogens emerge on a giant scale to take advantage of all the food (rat bodies) for their population to explode and mutate (like influenza, covid, etc., in humans). Rat diseases exist in nature every second of life,,, they don't become real apparent until their "food" (rats) becomes so abundant that it is noticeable on a scale us humans take note of. High populations lead to increased stress and most Biologists believe that stress decreases an animal's ability to fight off disease. Could also be an "eat out" of rats over producing their #'s for the available winter season food availability and starvation reduces their population. The mythical # K (Carrying Capacity) is used to evaluate the land / marsh's ability to support X number of critters per year 24-7. You use average climate, growing conditions, etc., to estimate that and in good growing years, with "seed" in place and easy winters, populations are above the K.............. Bottom line, End of the day, Boils down to--- the Seed must be in place, Area must be prepped with water conditions, Climate right during growing season, and Diseases / pathogens not highly present for Ma Nature to pull off a CROP................... Sorry I got winded............. Its Bio 101 and should not have spent so much of your time......... Look at it like a corn crop. We plant about 1/3 a bushel of seed per acre in a fertile seed bed in the spring, add some food through fertilizer and hope for good moisture and growing conditions with little or no disease to kill our population back. We hope to harvest 200-300 bushels/per acre and remove that "crop" (with the good and bad micro-organisms attached). If we left even 10% of that "crop" in place and we depended on it to repopulate our field like Nature does we may have a good next year or we may not and the environmental factors would be the MAJOR managers not US....................................... good luck this year as rats seem to be up and if they can immigrate or emigrate your areas, harvest heavy within areas of excellent habitat..................................... the mike

Right now I have seen some impact on the rat pop. Because of the little rain we got this summer but we still have enough to trap where I'm at

Along with stabile water, diseases, increased predators, bad Ag chems invasive European cattail will be another significant detrimental factor. Not only on m'rats.

The irony is despite the potential challenges some swamps cycle to explosion, while others continue to stagnate....

With drought as the exception!