Trip Report: Mexico City Area and Veracruz (Rodent-fest)

I was back in Mexico earlier this month to spend the weekend looking for stuff – mainly rodents – with Juan Cruzado Cortes (who helped me out in Oaxaca back in March). I was following in Venkat Sankar’s footsteps, visiting three sites he went to in 2016: Milpa Alta in Mexico City, and Totalco and Xalapa, about 4 hours to the east in Veracruz.

Juan brought 100 sherman traps with him, along with boundless patience and enthusiasm. Though we had mistnets we eventually opted not to catch bats this time – mainly because batting would be unproductive in Totalco and would likely catch little of particular interest to me in Xalapa.

Milpa Alta

My first stop – once I had found the taxi driver (a long – 2 hour long – story) – was San Pablo Oztotepec, near Milpa Alta, just an hour south of Mexico City airport. Juan was waiting for me at the cabin there after already setting sherman traps that evening in the community managed protected area on Volcan El Pelado.

At dawn we were driving up the track to check them along with several of the local conservation volunteers (from Grupo de Monitoreo Biológico de Milpa Alta) , a family member or two and a dog.

This is a beautiful spot. On the flat lands it is a mix of small grazing plots intermingled with patches of tussocky bunch grass, preserved as Volcano Rabbit habitat. And on the rocky slopes there is open pine forest.

It took about five minutes to see our first Volcano Rabbit (or Zacatuche as the locals call them): one scampered briefly along the road in front of the truck. I saw another three that morning while checking the sherman traps and without making a particular effort to look for them.

One posed well out in the open, though too far away for great pictures. And it was scared into the longer grass before I could approach closer. One of the world’s smallest rabbits, and arguably the cutest too, this species was my key target for the weekend.

After we had finished checking the traps I took a short wander to look for more Volcano Rabbits. No Volcano Rabbits, but I did see a Mexican Cottontail (which I didn’t photograph) and a couple of Eastern Cottontails.

A paddock next to the welcome sign (pictured above) was a mass of diggings of Merriam’s Pocket Gophers and Mexican Voles, both clearly abundant in the area. I got an untickable flash of what must have been a vole shooting down a hole. Further up the mountain we checked out more grazing land for both species. I didn’t see any voles but I did get a distant look through my binoculars at a Merriam’s Pocket Gopher sticking its head above ground.

Meanwhile, 100 metres away, some of the local volunteers were looking at a Long-tailed Weasel at the edge of the forest. The second they had seen that morning! Needless to say, I missed it. This is now officially my number one bogey animal now.

The small mammal trapping was fabulous and we caught good numbers of three species.

Mexican Volcano Mice, highly restricted to this area, were abundant and we caught more than 20 in our 100 traps.

We also caught several attractive Black-eared Deer Mice, a lifer for me.

Our final species comprised two Sumichrast’s Harvest Mice, distinctive with their very long tails (and another lifer)

There were a few extra possible captures up here including Volcano Harvest Mouse, but none of the potential species seemed very common from what I could gather. I was hoping to see a Peter’s Squirrel too, as Venkat had done, but these too seem fairly scare on the mountain. But I am not complaining: it was a gorgeous five lifer morning.

A big thanks for a really great few hours and reassuring to see the community protecting such special habitat and animals so well up there. A particular thanks to Juan’s friend Alejandra Hernández, who not only helped out with all the arrangements but was kind enough to drive us back into Mexico City…. in heavy traffic.

Totalco

Our next stop was Totalco, about 3 hours’ drive to the east of Mexico City. This is the place to see the endangered Perote Ground Squirrel and also a productive spot for small mammals, Long-tailed Weasels and more.

As Venkat mentioned in his report, the grassland here has been totally flogged. The majority of the short grass plains have been cleared to grow corn, and what isn’t planted is a dusty trash heap. Yet some Perote Ground Squirrels have managed to cling on: we saw several in the mid-morning in a remaining largish area of grass east of town.

We saw more the next day including a few in very degraded habit just west of town. So they are clinging on, and Juan said a new reserve had recently been establish to protect them. They are probably more common in the grassland patches inside the Mal Pais (“Badlands”) that flank the croplands here.

While scanning the grassland for ground squirrels I saw a pocket gopher outside its burrow. This was the second pocket gopher I had seen in 24 hours; not bad given I had never seen an untrapped pocket gopher before. I was able to approach this one quite closely: an Oriental Basin Pocket Gopher, a recent split from Merriam’s Pocket Gopher and very localised.

Juan had seen Long-tailed Weasels several times here, including two in one morning with Venkat. He has seen them primarily hunting along the edge of the mal pais so we spent several hours on two mornings cruising the tracks along the edge of that habitat in search of them. To no avail. Although many Rock Squirrels gave occasional cause for excitement.

Juan and I spotlit for an hour or so after dark from the car. We saw several Silky Pocket Mice (Perognathus flavus), the only small mouse in the area, and many Southern (formerly North American) Deermice running around the croplands. I also got a distant look at a pair of Phillps’s Kangaroo Rats on the edge of a field: much larger than the deer mice and with distinct bluish eyeshine. The only other mammal was a White-sided Jackrabbit, a species I have only seen once before right at the border of Mexico, New Mexico and Arizona

We set half of our traps in the mal pais habitat, next to the croplands north of town. After negotiating permission with a landowner we set 50 traps in among the rocks and cactus around here.

I don’t think I have trapped anywhere so productive: we had a 95% success rate!

A few traps around the farmer’s shack all contained Southern (formerly North American) Deer Mice.

In among the rocks the vast majority of traps contained Oacaxan Rock Deer Mice (Peromyscus amplus) (split in 2022 – at the time we recorded these as P. difficilis).

But it was going to be a long morning as we had to measure each and every mouse: the almost identical looking Perote Deer Mouse (Peromyscus bullatus) can only be separated from the Zacatecan flavour by checking the ear and feet length. In P. amplus the feet and ears are about the same length (23-25mm). But P. bullatus has larger ears (26mm and above) and smaller feet (24 mm and below).

The difference is slight to say the least … and several times I was sure we had got a big eared Perote Deer Mouse only to be proved wrong by the ruler.  After some 30 animals we caught one that Juan was sure was a Perote Deer Mouse!

We caught a second animal later. I had an inkling the tails of the two animals might be a bit different too, the tips in particular, with P. bullatus having a longer tuft of hair. But I am less sure about this after looking at the pictures.

Compared to this one.

We also caught three of my first Mexican Spiny Pocket Mice.

We set another 40 traps in the crop fields outside of town. We didn’t catch any of the Phillips’s Kangaroo Rats or Silky Pocket Mice I was hoping for; just a few more North American Deer Mice and Mexican Spiny Pocket Mice.

Xalapa

Xalapa is only an hour’s drive to the east of Totalco but it feels like a different continent. The desert and rocky badlands are replaced with cloud forest, and the attractive colonial town is a popular tourist destination.

Juan had arranged with Patricia MacSwiney, his buddy and a respected bat biologist, for us to set some traps on her block of land in Rancho Viejo, a small settlement in the forested hills on the outskirts of Xalapa.

We set our traps there, and more near our hotel – a peculiar place that was hosting some kind of a religious retreat. Lots of singing and chanting in the evening. Worse, I was rudely awakened from a siesta by a girl screaming, choking, gagging and wailing (yes, all at once) while her fellow faithful chanted around her. Very disturbing. Presumably some sort of exorcism. And an even worse sound to wake up to than most of the Iphone alarms. Thining back perhaps I should have had volunteered myself in the hope of breaking my Long-tailed Weasel curse.

There were several possibilities for the traps here including Blackish Deer Mice and Xalapan Pine Vole. We caught several of the former at both sites but none of the latter.

Next to a creek on Patricia’s land we caught two rice rats. The first was an Alfaro’s Rice Rat.

The second, a Northern Pygmy Rice Rat Oligoryzomys fulvescens, leapt straight out of the sherman trap before we could photograph it. Luckily Juan was confident of his ID from a quick glimpse.

Zoquiapan

Driving back to the airport we spent a little time around Zoquiapan, a national park and area an hour east of the airport. This is Mexican Ground Squirrel habitat, and the Mexican Ground Squirrel’s here are truly that species. The species in the SW USA formerly known as Mexican have now been split into Rio Grande Ground Squirrels.

We drove around for an hour or two looking at suitable habitat and were giving up to leave for the airport when I spotted an animal at the side of the road. Boom! My fourteenth lifer for the weekend.

As you might guess I am becoming increasingly enthusiastic about Mexico’s mammal watching potential, which is very largely due to Juan’s skill and hard work. Thank you again to him and to the others who helped over the weekend.

Trip List

White-sided Jackrabbit Lepus callotis
Mexican Cottontail Sylvilagus cunicularius
Eastern Cottontail Sylvilagus floridanus
Volcano Rabbit (Zacatuche) Romerolagus diazi
Mexican Ground Squirrel Ictidomys mexicanus
Perote Ground Squirrel Spermophilus perotensis
Variegated Ground (Rock) Squirrel Otospermophilus variegatus
Perote Deer Mouse Peromyscus bullatus
Oaxacan Rock Deer Mouse Peromyscus amplus
Blackish Deer Mouse Peromyscus furvus
Southern Deer Mouse Peromyscus labecula
Black-eared Deer Mouse Peromyscus melanotis
Western Harvest Mouse Reithrodontomys megalotis
Sumichrast’s Harvest Mouse Reithrodontomys sumichrasti
Mexican Volcano Mouse Neotomodon alstoni
Alfaro’s Rice Rat Handleyomys alfaroi
Northern Pygmy Rice Rat Oligoryzomys fulvescens
Merriam’s Pocket Gopher Pappogeomys merriami
Oriental Basin Pocket Gopher Pappogeomys fulvescens
Mexican Spiny Pocket Mouse Liomys irroratus
Silky Pocket Mouse Perognathus flavus
Phillips’s Kangaroo-Rat Dipodomys phillipsii

22 SPECIES, 15 lifers (in bold)