The article only describes them being eaten one by one, and does not describe how massive numbers are being eaten at once. The question seems reasonable-- how is the number 40,000 arrived at? Do you know? The article feels hand-wavy and light on sources and details. This feels to me like the kind of number that someone arrived at by assuming that a bear might eat its entire caloric intake in moths and then dividing 20k calories by 0.5 per moth, so it could be up to 40000 moths.
There's a sign on waterless urinals all over the place that claims it saves "up to" 40000 gallons of water per year. It'd have to be running non-stop 24/7/365 for that to be true. There's an ad that I hear playing on NPR sometimes about a container rail train that gets "up to" 500 miles per gallon. Just keeping the lights on uses more gas than that. These "statistics" don't pass the smell test, and this story feels similar to me.
The claim is that a train moves a ton of freight at 470 miles per gallon.
> Trains can move a ton of freight over 470 miles on a single gallon of fuel. [0]
The claim isn't that the whole train goes that distance in a single gallon. Each train can carry thousand to tens of thousands of tons of freight. So the train would need thousands to tens of thousand of gallons to go those 470 miles.
You might think that CXS's numbers are cherry picked, but this matches closely with the numbers of the US rail road industry as a whole which was 435.88 ton-miles per gallon of fuel [1]. The reason that trains are so efficient is that a relatively low speed train on steel wheels with steel rails minimises friction losses[2]. Once the train gets going it doesn't take much to keep it going.
I did some quick searching and found a Newsweek article with the same claim referencing a study where:
"White made that estimation by watching grizzlies with a scope for up to 14 hours per day, while writing his dissertation on the animals at Montana State University-Bozeman. He also counted how many dead moths he could find in each bear “scat,” or pile of poo, and multiplied that by the number of times these bears defecated."
>It'd have to be running non-stop 24/7/365 for that to be true.
The federal standard for gallons per flush for urinals is 1 (with some older models using 5 times that). If we're assuming, they're accessible 365 days/year, that's 110 flushes/day. Seems a little generous, but it's nowhere near as far off as you're claiming.
I remember the gypsy moth invasion of the 1980s. You could peel a few thousand off of one tree in my backyard. I have no trouble believing a determined bear could eat 40,000 a day if they were congregated like that.
The rail freight ad copy read on NPR was actually something like "Our trains can move a ton of freight 500 miles on a gallon of fuel." That ton-miles/gal stat makes a lot more sense when you realize that trains are VERY heavy. It's like comparing passenger-miles/gal for a car and a 747.
>The article only describes them being eaten one by one
From my reading, the article barely describes them being eaten at all. The black bear "licking moths off his arms" might reasonably be collecting a few at a time. Where does your interpretation of "one by one" come from?
> Just keeping the lights on uses more gas than that.
Can you elaborate on this?
One gallon of diesel = ~41kWh. Assuming 30% conversion efficiency that gives us 14kWh. Assuming a 50mph speed to traverse 500 miles means we need to keep the lights on for 10 hours, giving us a power budget of 1.4kW. I don't know what kind of lights locomotives carry but that seems like an awful lot.
locomotives have two headlamps around 200W, and two ditch lamps (the ones at the bottom near the rails) of 350 watts each. That's 1.1KW already, plus any interior lighting and conversion losses from the diesel genset.
Also average freight train speed is tracked and its consistently less than 25mph:
Note however that fuel efficiency is almost always given in mpg per freight ton, in which case the power usage of the lights would be amortized over the considerable mass of the train. >400 mpg per ton is not uncommon on a train.
It occurred to me that elevation change could have huge impact on those calculations. More back of the envelope stuff: a 5k ton train requires 13.6kWh to ascend 1m. If such elevation changes are common that would quickly dwarf small values like the power consumption of lights.
