whewww…. few days away at work & had a lot of pages to catch up on.
I wanted to respond to quite a few posts & the theories being raised/discussed. but I’ve come this far through all the pages that I’m not going back to find them!

These quoted posts are the most in line with my thinking. As well as one by
@RedHaus that I forgot to quote (again..not going back!)
I think the lightening is an interesting thought, but having grown up in the mountain west, dry lightning almost always started some sort of fire, either setting off the dry brush, or turning into a raging forest fire. Would ground lightening from many miles away eliminate risk of fire? I also question the notion of taking a lightning crouch & distancing space, if EC had enough time & cognizance of the strikes to get 30 yds away, wouldn’t one of them had time to remove the infant from the pack? I would think that leaving the child in a rigid pack that could stand on its own, so presumably has metal stantions, would that not leave your child at the greatest risk of all, as wouldn’t they essentially be attached to a lightning rod? yikes..
I personally find lightning less likely for that reason, as well as the fact that it overlooks the heat, but I would be able to entertain the idea of ground lightning as a 3rd possibility, maybe.
By 10AM it was dangerous for the dog to be 1.5 miles away from the car. My medical expertise only extends to animals, & I live a fairly childfree existence, but given what I know about neonatal/juvenile animals, I would say this risk extended to the infant as well.
The river was several miles away, from either direction of the loop. & looking at the topography, the trail “along the river” is actually up above it cut into the hillside. I am sure there are several little goat trail access points to some of the deeper pools, but it is not as if once they got down to the river that the trail meandered right next to, in fact it might be a technical little jaunt to access it.
If the family intended to get down to the river during the cooler times of day, cool off & splash around there throughout the heat of the day, & head back in the afternoon, as
@SpideySense has theorized, they would have had to get a much earlier start than 0800, unless they were planning on a very brisk jog down there, which seems unlikely given one of them was packing a child.
Despite sun position in the sky relative to the hills, heading back to the car, uphill, for several miles, at 4PM, would have been putting themselves performing strenuous activity in the absolute hottest part of the day (someone on thread #2 I believe posted hourly temps from El Portal). Just because the sun is not beating down on you, does not mean it’s shaded. Desert mountain valleys often “collect heat” & the ground is often radiating collected heat. This is a terribly dangerous plan for a dog full stop. The only way I could see this plan being survivable is if they planned to head back after dark (9-10PM), & if that had been their plan all along, with a baby & a dog, the parent not packing the child would likely have had to be equipped with a very large backpack to contain those sorts of provisions for that kind of full day adventure. There’s been no mention of their having this, so it seems faulty to assume, just as I’m sure others would think it’s faulty to assume they didn’t. LE quoted as saying they were “well prepared” could very easily just mean they had closed-toed shoes & a backpack with a bladder, which for a simple day hike, could be the truth. It’d be interesting to find out how this family prepared for their major treks through the Himalayas & Gobi - what kind of preppers were they? Months of research & planning; advice & recommendations from more experienced friends & family; or more spontaneous “we’ll figure it out as we go” type of attitude? I’m sure we’ll never know this, & I pass no judgement on any of the types (I probably fall closest to the latter camp myself), but I do think it does bear weight when considering “survivability” to some of the more extreme conditions one encounters in nature.
I understand wanting to keep the family’s best intentions at heart, but it requires suspending way too much disbelief about their level of preparedness & possibly even their intentions. IMO there was no way to recreate in this area safely with a pet the time of day they were out & in the environment they were in.
I said this further back thread, but they only way I could see this being safe, with a dog, in this location, with a departure time after 0800, is if they had turned back to the car after traveling 1/2 mile, factor in the infant & I’d say it’d be safer to turn back after 1/4 mile.
When my late best friend (canine) was decompensating from a neuromuscular disorder, I began relying heavily on my garmin watch to log our distance to make sure we didn’t overdo it, because I learned early on in the process that often she’d still have the energy to keep going, but if I let her lead the charge, she’d be hobbled on the way back & debilitated that night. The data was actually really tragic to look at, because I could see where we started having to turn around at 2 miles, then 1 mile, then 0.5 mile, then 0.25 mile in a span of several months. Kind of a major aside, but I think my point being is that dogs, even dogs with debilitating conditions, will often overexert themselves & express no cognizance of their limits until it is too late.
MSM quoting LE on saying “there was a small amount of water in a bladder” is inconsequential. A small amount of water could be enough to hydrate a human, enough to test, a small amount of water could be residual after the bladder had been open & dumped on an overheating family member. Some of the bladder designs have a lip which make it almost impossible to effectively purge them of water (my personal conspiracy theory is this is an intentional design flaw to promote mildew & hence new bladder sales..ha). As other posters have said, heatstroke & dehydration are 2 different beasts that often play together, but one can act without the other. The amount of water in a single bladder would not be enough to cool an overheating dog, particularly at room temps. Submersion in the river might help, if done right at onset of heat exhaustion signs, however the river was several miles away, & we don’t know the access points. I know another poster has stated this, I think
@NSamuelle , but I’ll say it again. Heat related injuries start with heat stress, progress to heat exhaustion, & finally heat stroke. You should be getting out of the heat promptly at signs of heat exhaustion. Once at the level of heat stroke you have roughly 30 min. to reverse the process. One poster shared a really exemplary story of hiking to an alpine lake with their friend who sat down for a break & then quickly became delirious, had 2 other hikers not come along & helped them carry their companion to a lake to submerge him, he most assuredly would have died where he sat.
This process (from heat exhaustion to stroke) in a canine, happens much more rapidly than in a human, & is very often disregarded in them because it seems more subtle to those that are not hyper vigilant about the risks. Essentially the dog would be panting (easily ignored, all dogs pant in heat & activity) & slowing down. I have treated (& failed at treating) many a heatstroke that occurred because the person just thought the dog was tired & pushed them beyond ability. Being an active & athletic dog does not make one immune or less susceptible to heat related injuries, which is another thing that is often a misconception. Things like age (being < 1 yr or > 8 yrs), body condition, coat length/density/color, & muzzle length can exponentiate the risk.
My last response that is coming to mind at the moment, is to someone that asked about heatstroke & autopsies showing evidence of multi-organ failure. Heatstroke can cause death via many processes, multi-organ dysfunction being only one of them. Death via failure of the central nervous system can occur prior to arriving at a state where organs fail, in layman’s terms: the brain gets cooked before the organs do. Heatstroke can kick off a terrible coagulation progress called disseminated intravascular coagulation (DIC), or as one my pathology professors taught, “Death Is Coming”, where the body begins abnormally producing microvascular blood clots, & consuming platelets & clotting factors to do so. This process is complex & nearly irreversible (in vet med at least even at advanced facilities), but one essentially dies from this via blood clot to vital organ or hemorrhage. Depending on where you die in the process & when postmortem samples are collected, it could be difficult (but not impossible) to diagnose at necropsy. General rule of thumb is that if you want to find out why an animal died, you get the body cooled, not frozen, & overnighted to the pathology lab, & even then I’ve seen results be fairly inconclusive. Extreme heat & extreme cold after death can greatly impact definitive diagnoses when the answer lies in the tissues. And at normal temperatures, time is going to be a factor as regular old run of the mill decomposition is going to confound results.