“Can red wigglers and European Crawlers coexist in the same basic bin?” ~ Jim E
In terms of co-existing alone, the answer is yes.
I was reading some research papers the other day about the concerns of the introduction of exotic (foreign) earthworm species into American land.
I’m not going to go into the environmental and ecological risks in detail, but a section mentions that “There is evidence that native earthworm populations can coexist with exotic earthworms and in some instances may have an advantage if the site is not highly disturbed” (James, 1991; Dotson and Kalisz, 1989; Callaham and Blair, 1999; Callaham et. al, 2001).
Having said this, Red wigglers (Eisenia Feotidas) and European Crawlers (Dendrobaenas) are both not native to North America, but the point is they can live happily side by side together.
Although they can both co-exist, if you are looking to breed worms, I will suggest you separate them and not breed them together.
This is for the benefit of the European Nightcrawler because they are larger, worth more by the pound and they also breed slower.
The two type of worms have quite different characteristics in terms of birth cycles, environment adaptability and sexual maturation.
Under optimal conditions for Red wigglers, from the time of birth to sexual maturity ranges from 21-30 days, where then the frequency of depositing a cocoon is 0.35- 1.3 per day. Each cocoon hatches 2.5-3.8 worms (Earthworm Ecology, C.Edwards 2004). Their temperature range is 18°C – 28°C and can live up to 5 years.
On the other hand, European Nightcrawlers do not grow as rapidly, but is more robust and can adapt to a wider moisture range. It takes an average time of 65 days to reach sexual maturity and even then they only produce 0.28 cocoons per day. They also prefer a cooler temperature range of 15°C- 25°C.
So what does all this data mean?
Since red wigglers are much more prolific in reproduction, at room temperature (25°C) you will very quickly have a bin dominated by red wigglers. Sure, the European Nightcrawlers will still grow, but worms cannot cross breed and can only breed with their own species. So with more red wigglers around it will lower the chances of European Night crawlers finding their mate to breed.
Having a dominance in red wigglers will also mean a competition in resources. Worms do the clever thing in being able to control their population, which means another limitation for the chances of European night crawlers to proliferate.
If it sounds like the red wigglers will always win, that’s not necessarily so.
If the conditions are different (say lower temperatures or lower moisture content) then this may favor the Nightcrawlers.
Red wigglers are more of the type to be adventurous and go explore, where European nightcrawlers are more of the conserved type which likes to stay where they are until it becomes life threatening. So in unfavorable conditions you may see red wigglers disappear leaving a few European Nightcrawlers around.
So to conclude, separating the two species is the best way to go if you’re breeding (doesn’t matter as much if you’re only thinking of composting). It will give you more control over the species you’re breeding and taking care of their individual needs to give them optimal conditions.