New World ID questions

Several people told me this is the best place to try to crack my trickiest ID questions, so I hope this is not too much of an abuse of this community … because I do have a lot of those, interestingly almost exclusively related to the Americas – both North and South.

As the forum layout doesn’t seem well suited to a lot of pictures in one post, I made them into an 8MB PDF containing 27 pictures, almost all from the US and Argentina with some bonuses from Peru and Mexico. Any insights would be most welcome!



  • Jose R. Castello

    Here you have my two cents on your Canids:

    11 and 12. – Pampas Fox (Lycalopex gymnocercus antiquus). However, some authors have suggested it is conspecific with South American Foxes (Monte Desert Chilla, L. griseus gracilis), on the basis of craniometric and pelage character analyses, and that both forms are clinal variations of one single species (L. gymnocercus). In general, L. griseus has more uniform gray pelage, but otherwise very similar.

    13 and probably also 14. South American Gray Fox (Patagonian Chilla, Lycalopex griseus griseus). Generally, Culpeo Foxes have a larger area of white on the chin, and the black spot on the lower side of the rear side of the hind limb is inconspicuous. And are larger (but this cannot be evaluated in the photograph).

    15. South American Gray Fox (Monte Desert Chilla, Lycalopex griseus gracilis).

    • JanEbr

      Thanks, this has been bugging me for years! So my observation that Pampas Foxes seem very similar to some SA Foxes was not completely unfounded. Still, as IUCN keeps Pampas Fox as separate species, I would follow it in my list for now for consistency, so it’s great that you could ID them! I would have been said that none of the candidates is Andean Fox, but luckily we have one other from Bolivia from an area where no other fox occurs within hundreds of kilometers.

  • Alvaro Jaramillo

    Guinea Pigs, the thin ones with a bold eye ring and seemingly long legs are Microcavia. 20, does not look like Microcavia.
    25-26 – Peale’s Dolphin
    27 – Looks good for female or young Pacific White-sided Dolphin. Swept back, and bicolored. However, I did not know they got that far south.

    • JanEbr

      Thanks! If 20 is not Microcavia, than it surely has to be Galea leucoblephara (this is a little bit confusing in taxonomy to me, as some people put it as a ssp. of G. musteloides, but IUCN doesn’t) – there is nothing that looks even remotely similar in deep inland Argentina to my knowledge. Pacific White-sided Dolphin is indeed reported along the whole Baja California it seems, so that would be a great fit.

  • Venkat Sankar

    For the kangaroo rats, the #2-4 look like Giant. #1 looks like San Joaquin (D. nitratoides). That said, Heermann’s vs. Giant is really hard and if you want to be sure, best to see Heermann’s somewhere where Giant doesn’t occur (e.g. Lonoak Road). Usually, Giant K-rat is a dominant species that forms large, single-sp. colonies and Heermann’s does not co-occur at the exact same site. Hence I doubt you’d see both side by side (I think Heermann’s is more abundant in the far S of Carrizo Plain, where Giant is rarer).

    #5 is Ord’s (I don’t think Merriam’s occurs as far N as Canyonlands).

    #6 is probably Merriam’s. Buenos Aires NR is too far West for Ord’s I think, at least the database I use has no collection records of Ord’s from W of Patagonia, only Merriam’s.

    #7 is almost certainly White-throated. Mexican is only in pine forest in the high Chiricahuas in that area, and is less bright white.

    #8 I guess San Diego, as Desert PM strongly avoids boulders and even gravel. Could be Spiny however, though the spines don’t look pronounced enough for that species.

    #9 probably some Myotis, but not sure
    #10 looks like Canyon Bat to me too

    I’ll leave South American stuff to other people who have expertise in that area.

    #27 looks like Pacific White-sided Dolphin. It’s common in coastal areas throughout CA, and I’ve seen it from shore once.

    • JanEbr

      Thanks! I am courious about #1 then – because while I admit that our method of measurements is a bit wonky, it gives a pretty good lower bound (it can easily underestimate, but it’s hard to overestimate) and then the tail length is outside the upper bound for San Joaquin. The “Giant” k-rats were indeed seen in one large colony, reinforcing the idea of them being Giant. The other arguments are sound – IUCN shows both Ord’s and Merriam’s in BA, but if you have better data, IUCN maps tend to be not too precise.

      • Venkat Sankar

        Yes #1 was a bit problematic for me too. The tail length does seem to be above the upper bound for SJ.

        Could be a juvenile Giant K-rat (looks pretty different from an adult). I highly doubt it’s Heermann’s, as that has a tail with black lines on the top and bottom. This one only has the black along the top, suggesting it’s either Giant or SJ.

  • Jon Hall

    On the Armadillos then people familiar with the species have little problems in differentiating them. I am not familiar with the species so you might want to check with an Argentinian mammal person. I am pretty sure 22 is a Large Hairy Armadillo. Unsure on the other two though – I would guess they are both large hairy too but that is very much a guess.

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