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In populating a fenland region similar to the Somerset Levels in England, I'm finding a need for an aquatic ambush predator to haunt the region and snack on the occasional disrespectful traveler who forgets to make the appropriate sacrifices. It's a role that's traditionally filled by crocodiles in more deserty cultures, but what could do that job in the higher latitudes?

If there's a real, extant animal that can do the job, that's ideal, I just can't think of one. If there's a real, prehistoric animal that filled the niche, that's the next best thing. If necessary, I'm not above making something up, but I'd rather keep things based on reality.

So - what animal could function as an aquatic ambush predator in a northern European climate?

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    $\begingroup$ What about a pike? I do not really understand why you'd need a huge aquatic predator that can hunt down bigger game that doesn't really roam in these areas, so I'm just putting out a comment... also pike fish aren't that big, but they can be nasty $\endgroup$
    – dot_Sp0T
    Commented Dec 29, 2016 at 20:20
  • $\begingroup$ Is the existence of the particular niche crocodiles inhabit not a product of a warm climate? $\endgroup$ Commented Dec 29, 2016 at 21:59
  • $\begingroup$ @dot_Sp0T I have to admit, the idea of a giant pike haunting the swamp is extremely tempting - definite mythical aspects. Care to make that an answer? $\endgroup$
    – Werrf
    Commented Dec 30, 2016 at 13:10

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Trick question! Somerset is pretty warm!

Here is the range of the American Alligator. Wilmington, NC is clearly within the alligator's range. Here is Wilmington's climate, and here is Bath, the closest city to the Somerset levels with record high and low temps on Wikipedia.

The mean low in Wilmington is 2 C and in Bath 1.9 C. The record lows are -15 C and -14 C, respectively. So it is not necessarily 'too cold' for alligators in Somerset.

Now, Alligator aren't really very active below 20 C, so cool summer temperatures in Bath aren't very conductive to crocodillian life forms. On the other hand, some hold the opinion that crocodillians evolved from a warm-blooded common ancestor with birds and dinosaurs. If that is the case, it isn't much of a stretch at all to imagine one line of alligator-like creatures surviving to the present with improved ability to thermo-regulate, if not full on endothermy.

The important point is that swamps in Bath, like the swamps near Wilmington, do not freeze hard in the winter. That is the key development that would make the alligator life-style untenable; they'd have to get out of the water for some months of the year and hide/hibernate. For young alligators, the pressure from medium sized carnivorous land mammals (racoons, badgers, foxes, coyotes, etc) would destroy them quickly ( 1 year old alligators are in the 10-18 inch long range; in the cold they'd be easy pickings). But with young able to stay in the relative safety of the water all year, the species becomes more viable.

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  • $\begingroup$ Interesting info, thank you! I couldn't find a clear answer on how far north crocodilians roam, I never would have expected it to be as far as NC. $\endgroup$
    – Werrf
    Commented Dec 30, 2016 at 13:11

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