Rodents farmed for pet snake food

post by saulius · 2019-02-20T19:54:28.356Z · EA · GW · 14 comments

Contents

  Summary
  Context
  Estimating how many animals are killed for snake food per year
    of pet snakes
    number of animals fed to snakes
    of animals killed for snake food each year (first calculation)
    alternative estimate that uses frozen rodents sales
  Snakes farmed for other purposes
  Lifespan of breeder mice
  Welfare concerns
    for feeder mice
      Lack of space
      Living in their own feces
      Lack of shelters
      Lack of activities
      Lack of daylight
      Possible lack of bedding and nesting material in some cases
      Possible lack of veterinary care
      Lack of regulations (at least in the U.S.)
    live prey
  Possible interventions
  Endnotes
  References
None
14 comments

Summary

In this article, I first estimate the number of animals raised for pet snake food in the world. Then I discuss some welfare concerns of these feeder rodents by comparing the conditions in which they are raised to the ones recommended for pet mice. Finally, I brainstorm about possible interventions.

Context

This article is a part of a series of articles by Rethink Priorities about animals farmed for various purposes. We are also planning to write about fish farmed for fish stock enhancements, and considering writing about the mortality of farmed food animals. Finally, we will create a list of estimates of numbers of animals kept in captivity for various purposes. After that, we may create a similar list of estimates of numbers of wild animals humans affect in various ways. The main goal of the series is to uncover sources of animal suffering that other organizations could tackle with cost-effective interventions.

After writing this exploratory article about feeder rodents, I remain largely uncertain about the scale and especially the tractability of this problem. I look forward to reading opinions about it in the comments.

Estimating how many animals are killed for snake food per year

In this section, I'll produce two different 90% subjective confidence intervals of numbers of vertebrates killed for pet snake food and combine them into one:

For brevity, in the article I use K for a thousand, M for a million, and B or a billion. Many details of the estimations can be seen in the Guesstimate model. Readers who are uninterested in the details of the calculation can skip this section [EA · GW].

Number of pet snakes

I haven’t found any estimates of the number of pet snakes in the world, but I have found some estimates for various countries:

Using this information and some other information, I estimated that there are between 3.8M and 6.9M pet snakes in households around the world. See my guesstimate model for the estimation. The model includes guessing the number of snakes per 1000 people in countries for which I couldn’t find statistics.

Some snakes that are bred to be pets are in pet stores and snake breeding facilities. For example, in Blackpool, UK (population 140K) there are at least two shops that sell snakes. I visited one of them and counted 126 snakes on its shelves, which is almost 1 per thousand people. This shows that the number of snakes in pet shops is significant. I guess that the percentage of such snakes that are yet to be purchased is somewhere between 3 and 20%. With this taken into account, I estimate that there are 4.2–7.8M snakes that are bred to be pets.

Average number of animals fed to snakes

How often snakes are fed depends on species. It seems that for all species, young snakes should be fed smaller mice more often. For example, according to a ReptiFiles.com article, Corn Snakes have to be fed 1–3 smaller mice every 7–10 days until they are 18 months old (number and size of feeder mice depend on age). Ball Pythons should be fed every 5–7 days when they are young. However, snakes spend most of their time being adults. This page lists the five most popular pet snake species. Here is how often each of them should be fed as adults:

It’s possible that some owners choose to feed adult snakes multiple smaller mice rather than one big mouse/rat. Or that some people feed them more often than guides suggest. Manual of Exotic Pet Practice mentions that “snakes are often overfed in captivity.” This informal poll shows that many owners feed one rodent per week and quite many feed more. I also asked how often snakes should be fed at one reptile store and I was told that almost all of their snakes are fed one mice of appropriate size per week, while few bigger snakes are fed more often.

Note that mice are not the only animals snakes eat. A PetHelpful article claims that there are pet snakes that eat chicks, fish, insects, eggs, and reptiles. VCA Animal Hospitals claims that the most popular pet snakes usually eat prey such as mice, rats, gerbils, and hamsters. Larger pet snakes will also eat whole rabbits. At the extreme end, this itv news report about possibly the longest pet snake in the UK claims that it eats 3 rabbits per week.[1] Based on all this information, I guess that on average pet snakes eat 0.6–1.8 vertebrates per week, which is 31 to 94 vertebrates per year.

Number of animals killed for snake food each year (first calculation)

To calculate it, I multiply the number of snakes in the world by the number of animals they eat per year. I also guess that 3%–20% of snakes kept to be pets are in pet stores and breeding facilities. After taking that into account, I get a 90% subjective confidence interval that there are 160M–580M animals fed to pet snakes per year.

An alternative estimate that uses frozen rodents sales

I found some sources that directly say how many frozen rodents are sold. They are much higher than I expected:

Even if FBH’s estimate of the number of pet reptiles is incorrect, it’s possible that the sales of reptile food data that was used to produce the estimates is correct. However, in that case, there is an inconsistency between PFMA’s estimate that there are 200K–400K pet snakes in the UK and FBHs claim that 1M–2M frozen mice sold are sold each week because that would be 3–8.5 frozen mice per snake per week - much more than average snake eats. Similarly, if we assume that in 1999 there were as many snakes in the U.S. as in 2007 (586K) and that figures in the Independent article are correct, that would mean that in the U.S. there were 5.5 rodents raised per snake. There are multiple ways to explain these inconsistencies:

In the end, even though I don’t trust FBH’s numbers, I don’t trust my estimation in the previous section much either, and the FBH’s numbers are the only direct rodent sales numbers I found.

In the guesstimate model, I use FBH’s numbers to produce an alternative calculation. First I calculate the number of rodents fed to pet snakes in the U.K. To do that, I multiply FBH’s figures (1M–2M frozen mice per week which is 52M–104M per year) by the proportion of frozen mice that are sold as food for pet snakes. As mentioned before, frozen mice can also be used to feed to some other pet animals, and used at zoos and wildlife rehabilitation centers. I don’t know the value of this proportion is, but I guess that it is between 50% and 97%. I then divide it from the proportion of vertebrates produced for pet snake food that is frozen mice. As mentioned before, some snakes are fed rats, chicks, rabbits or other animals but farmed mice seem to be by far most popular, at least in the U.K. Consequently, I guess that the proportion is between 80% and 95%. Finally, I use my estimate that 4–9% of world’s pet snakes are in the UK, to estimate that 540M–2.1B vertebrates are killed for pet snake food in the world each year. Note that I assume that the ratio of snakes to mice in the UK and the world is the same, which might not be correct. Furthermore, I could have incorrectly estimate the proportion of pet snakes that live in the UK.

This estimate barely overlaps with my previous estimate that 160M–580M animals fed to pet snakes per year. This makes me doubt both of my models, so I take the lower bound from one estimate, and upper bound from the other, and end up with a 90% subjective confidence interval of 160M–2.1B vertebrates are killed for pet snake food in the world each year. For comparison, Prize (2014) estimates that around 118M animals are used for experiments, although it claims that this is likely an underestimate. It seems that most of the vertebrates fed to snakes are farmed mice, though I’m not sure what the percentage is, especially outside of the U.K. and the U.S.

Snakes farmed for other purposes

Pet snakes are not the only snakes in captivity. This Business Insider article claims that one Chinese village breeds 3M snakes per year for food and venom (which is used for medicinal purposes). Snakes are also farmed for their skins. I was unable to get an estimate of how many snakes are farmed for other purposes in the world due to the lack of statistics. It’s also unclear how many of these snakes are fed farmed rodents. Here is all the evidence about the feeding of snakes that are bred for purposes other than companionship that I have found:

Overall, it’s unclear how many of snakes farmed for other purposes are fed farmed mice but it seems that farmed mice is not the most common food for these snakes.

Lifespan of breeder mice

To determine the scale of suffering endured by feeder animals, we need to consider not only the numbers but also how long on average animals live and suffer in factory farm conditions.

Hardin (2013) shows that these rodents can be slaughtered when aged anywhere between 48 hours, to 9 or more months. It also claims that “most feeder rodents typically are sold before or shortly after weaning.” Mice are weaned between 21–26 days of age. Judging from what I see in online stores, I guess that a considerable number of mice are also killed at a different age (both younger and older). A veterinarian told me that at one zoo, some small raptors/reptiles were fed younger mice, but in general, mice were killed (or fed alive) at 8–10 weeks of age

Welfare concerns

In this section, I look at conditions in which feeder rodents live in farms and compare them with the conditions that are recommended for laboratory and pet mice. Then I briefly discuss concerns about live feeding.

This section was reviewed by a veterinarian who wished to remain anonymous. They confirmed my impression that conditions seen in the videos and pictures below are bad. They also told that conditions for feeder rodents they witnessed at a zoo and at a pet store were similar.

Conditions for feeder mice

I’ve only found several videos and pictures of conditions in feeder mice farms:

Picture 1:

Picture 1

Picture 2:

Picture 2

Lack of space

RSPCA guidelines for keeping pet mice explain that “wild mice can have very large territories. Mice need sufficient space to display natural behaviors and give control/choice over their environment.” petsworld.co.uk claims that the minimum cage size for a pair of pet mice is 45cm x 30cm (1350 cm2) with at least 25cm depth.

Fawcett (2012) has these guidelines for the housing of mice in scientific institutions:

“As a guide, enclosures should allow for a minimum floor area of 250cm2 for a single housed mouse, a minimum floor area of 500cm2 for two mice and ensuring a minimum floor area of 60cm2 per additional adult mouse when mice are housed in larger groups.”
“As a guide, the optimal size for a group of adult mice is three to five for females and three for males.”

In video 1 there are 50 mice in a box that seems to be smaller than 1800cm2, maybe even 1000cm2. In some other videos the situation appears to be better, but in video 3 and picture 1 it is much worse.[4]

Living in their own feces

A veterinarian said that in most of the videos a lot of feces can be seen within the bed of all the drawers. Pet mice usually choose a toilet corner, but it doesn’t always happen. I find it unlikely that all rodents pick the same corner when living in such cramped conditions. And even if they do, feces might accumulate quickly. In video 2, the man claims that he cleans containers every “week or week and a half.” According to this page, this might be insufficient even when mice are not cramped.

Lack of shelters

Fawcett (2012) gives detailed instructions for shelters that have to be provided to lab mice. Similarly, RSPCA guidelines explain that “mice are a prey species; they’re highly motivated to stay near cover.” It claims that they need tubes for hiding or sleeping in, shelters with multiple exits where mice could hide when they wish, and avoid any confrontation with other cage mates. In all cases, cages for feeder mice don’t include any shelters.

Living in such cramped conditions without places to hide might be causing a lot of stress to mice, especially if some of them become aggressive. Both, RSPCA and Fawcett (2012) claim that mice should always be monitored to check that cage mates do not become aggressive. I haven’t seen any indication that this is being done in breeding facilities.

Lack of activities

Fawcett (2012) claims that “environmental enrichment is essential for all mice.” Similarly, RSPCA says that “running wheels can be provided but shouldn’t be the only enrichment.” Lack of any enrichment in containers is concerning.

Lack of daylight

RSPCA also claims that mice need natural daylight. However, in all videos, they are only exposed to artificial light and in video 1 they seem to spend their time in darkness.

Possible lack of bedding and nesting material in some cases

RSPCA claims that “mice need bedding material to dig/absorb moisture from urine/faeces” and nesting materials are needed to help body temperature regulation. Bedding materials seem to be present in videos 1, 2, 4 and 5, but they seem to be lacking in video 3 and in picture 1. However, it’s possible that video 3 does not show the environment in which mice spend most of their time. I can’t tell whether nesting materials are provided in any of the videos.

Possible lack of veterinary care

It’s unclear whether rodents receive veterinary care when they need it, but I'd be surprised if they do. A veterinarian said that even when sold as pets, mice are often filthy and don’t always receive adequate medical care.

Lack of regulations (at least in the U.S.)

Hardin (2013) claims:

“Unlike other rodents, rats and mice are not governed by the Animal Welfare Act (USDA 2013) and thus are not subject to federal regulations on caging, transportation and handling. Nonetheless, successful producers generally adhere to professional standards of husbandry. As with any industry, there have been a few operations with unsanitary conditions and substandard care and housing, along with a few unusual incidents, which has cast a negative light on feeder rodent producers. Additionally, feeder rodents have been vectors in zoonotic outbreaks, e.g., salmonellosis, lymphocytic choriomeningitis virus (LCMV), rat bite fever.”

The fact that mice conditions are not regulated in any way makes me concerned. However, in the U.S., no federal laws govern the conditions in which farmed animals are raised either.

Feeding live prey

All the articles I’ve seen advise against feeding snakes live prey. Rodents can injure (sometimes even kill) the snake and cause infections.[5] Despite that, it seems that a significant number of owners are doing it because wherever snake food is discussed, live feeding is discussed as well. I haven’t found any statistics on what percentage of animals are fed alive,[6] but according to Hardin (2013), the majority of animals are sold frozen (rather than live). It claims that this “avoids degradation in the quality of live animals from transport stress.” In addition to stress during transport, animals may suffer while they are kept in a pet store. In this article, a person who used to work at a pet store told that she witnessed ill or injured feeder mice on a daily basis. She told that other workers did not care about their welfare, once dismissing her concern about an open wound because it was “just a feeder mouse.”

Finally, there is also suffering during feeding.[7] As I understand it, most of the time snake will kill prey very quickly. By looking at 20 YouTube videos of live-feeding, Cooper and Williams (2014) estimated that “the time to death as estimated by cessation of any movement was 62 ± 29 seconds for mice, 54 ± 21 seconds for rat”. However, in some cases, snake may not be hungry, and a rodent could be stuck in a tank with a predator for days.

Possible interventions

Here are some possible interventions to reduce the suffering of these animals:

My intuition is that trying to ban the sale of snakes in pet stores is the most promising intervention, but I'm very uncertain. I also don’t know if any of these interventions would be cost-effective compared to ACE’s top charities.

Endnotes

[1] It also claims that the snake might live for up to 30 years. That means that over its lifetime it might eat over 4K rabbits.

[2] According to AVMA (2012), there are 1.15M snakes in the U.S., owned by 550K households. According to the same source, in 2007 there were 586K pet snakes in the U.S. This 2018 article claims that herps (non-avian reptiles and amphibians) are becoming increasingly popular and mainstream and that sales of their food are increasing. This 2013 Pet Age article claims that “over the past 25 years, the feeder rodent industry has grown substantially”.

[3] Furthermore, I find it hard to believe that there are more pet reptiles than dogs in the UK.

[4] The box in video 3 is tall but as this page (written by a hobbyist) explains:

“tall aquariums are a poor choice, for instance, because mice can't enjoy the space - they need room to run around, not look up at. Not only that, but air circulates poorly in a tall aquarium.”

The page also recommends to use a 20-gallon aquarium for a group of five or six mice.

[5] In a pet store I was told that feeding live mice is illegal in the UK due to animal welfare concerns. If that is really the case, it shows that legislative progress in this area is possible.

[6] According to slide 72 of this presentation:

"34% (83/246) of Minnesota Salmonella cases who reported reptile exposure reported feeding their reptile some type of rodent – 87% (72/83) of snake owners reported feeding them rodents. Among those who fed rodents: – 59% (47/80) fed frozen rodents – 41% (33/80) fed live rodents."

However, this is not a representative sample and live mice may be more prone to cause salmonella.

[7] Cooper and Williams (2014) describes welfare issues with live feeding:

[8] I think that such campaigns could gain public support because the suffering of feeder rodents is more obviously unnecessary than the suffering of animals raised for human food or used for experiments. Non-vegetarians would feel less cognitive dissonance about supporting it. Furthermore, fewer people doubt rodents’ ability to suffer than chickens’ or fish ability to suffer. Rodents are also often featured in campaigns against animal testing which is a cause that has received a lot of attention relative to its size. This indicates that people can care about rodents even if they don’t seem like the most popular animals.

References

The American Veterinary Medical Association. 2012 U.S. Pet Ownership & Demographics Sourcebook.

Aust P., Tri N. V., Natusch D., Alexander G. J. 2016. Asian snake farms: conservation curse or sustainable enterprise?

Clark, B. 2012? A Report Looking at the Reptile Keeping Hobby, Those Who Want it Banned and Why?

Cooper, J. E., Williams, D. L. 2005. The Feeding of Live Food to Exotic Pets: Issues of Welfare and Ethics

ENDCAP (2012). Wild Pets in the European Union.

Hardin S. 2013. Best Management Practices for Feeder Rodent Production and Distribution.

Prize, L. 2014. A global view of animal experiments 2014.

Fawcett, A. 2012. Guidelines for the housing of mice in scientific institutions.


This essay is a project of Rethink Priorities. It was written by Saulius Šimčikas. Thanks to Daniela R. Waldhorn, Marcus A. Davis, and Peter Hurford for reviewing drafts of this post and making valuable comments.

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14 comments

Comments sorted by top scores.

comment by kierangreig · 2019-02-21T20:57:35.598Z · EA(p) · GW(p)

Thanks for writing this up Saulius! I think it is a really useful addition to the literature on EAA. You seem good at writing such content! :)

Some very quick thoughts that I had on this piece:

- My rough impression is that the “pre-slaughter mortality rate” of mice is relatively high. This matches my own experience when I had pet mice when I was younger and a quick google suggests that lab mice mortality seems high. E.g.
> We examined the survival rate of 539 litters of mice from two of the most commonly used laboratory strains (C57Bl/6 and Balb/c) bred under normal husbandry procedures, and found that mortality rate (that is whole litters lost) was at average 28,9%.

- My rough impression is some pet snakes feed on eggs or fish predominantly rather than mice. I am not sure how big a proportion does that though but it could be significant. E.g., I think the Gartner Snake is a fairly common pet breed and that it is common to feed them fish.

- I have a feeling that rodents are farmed in larger numbers for human consumption in some asian countries but a quick google didn’t really confirm or deny that.

- I wonder if more mice are fed to captive/farmed crocodiles, alligators, and caimans then to captive snakes. These other reptiles are are much bigger than the average snake and eat more often, and I think it is common to feed them mice. Skimming this and it seems possible that the number of these other reptiles farmed is in the hundreds of thousands.

-I wonder if mice are fed in quite large amounts to captive predatory birds. E.g., this suggests one of these birds eats x5 the amount of mice p/w than a python does.

- I thinks there’s a decent chance that if one were to dive deeper into the farming of invertebrates then this could lead to discoveries of tens of billions of additional farmed animals the movement largely currently neglects.

But in all I mainly think this is an important area that not many have thought about (including me). Thanks for highlighting it! :)

comment by SiebeRozendal · 2019-02-27T14:40:42.683Z · EA(p) · GW(p)
I thinks there’s a decent chance that if one were to dive deeper into the farming of invertebrates then this could lead to discoveries of tens of billions of additional farmed animals the movement largely currently neglects.

I agree.

Say this is the case, what would be the implications? It does seem that more general anti-speciecism efforts become comparatively more effective the more animal suffering is widely dispersed.

comment by AviNorowitz (AviN) · 2019-02-21T13:42:50.284Z · EA(p) · GW(p)

Thanks for working on this! I'm impressed by this and your other work [EA · GW] on identifying and investigating groups of farmed animals that exist in large numbers but have been overlooked by other EAs, researchers, advocates, etc.

comment by Aaron Gertler (aarongertler) · 2019-02-20T23:59:02.642Z · EA(p) · GW(p)

This is a really good analysis! Thanks for posting.

A few notes I thought of as I read:

  • You state that you're worried about campaigns to stop or prevent snake ownership possibly increasing publicity around pet snakes and increasing their numbers. I think you could try to estimate this effect by looking at similar cases of "negative publicity against a certain pet".

  • For example, when a pet dog kills someone in a way that gets widely reported, do sales of that dog breed tend to go down, or up? Did this story lead to less python ownership in the UK? (These numbers may not be possible to find, but since this question may apply to other CE analyses around pet predators, seems worth a shot!)

  • Since RP is considering interventions to prevent mouse suffering, are there plans to look at changing agricultural policy to protect field mice? This article estimates 6-40 animals killed per acre of grain, per year (seems to be mostly mice), but notes high uncertainty around both the number and the counterfactual outcome for these animals.

  • I didn't see you mention "recommending alternative snakes" as a possible intervention. Even if all the most popular snakes are whole-animal carnivores, I wonder how many people who want to buy a snake would be open to choosing one that eats insects or eggs, rather than whole mice? (I'm not sure how insect/chicken suffering would be affected by this choice, but intuitively it seems less bad than raising so many mice in such poor conditions.)

comment by saulius · 2019-02-21T00:56:38.806Z · EA(p) · GW(p)

  • This post is by Rethink Priorities (RP), not Charity Entrepreneurship (CE)! These two organisations are not affiliated. RP does foundational research on neglected causes. CE aims to create high-impact charities.
  • My worry is that many people might not even know that owning a pet snake is a possibility. Any publicity about this issue could make more people aware that they can own snakes, which could lead to increased sales of pet snakes. I don’t know if this concern is valid, it’s based only on my intuitions, and your intuitions are as good as mine here. Everyone knows that dogs can be pets, so the situation is not analogous. Unfortunately, the impact of news stories on snake ownership can’t be evaluated because there is not enough data about snake ownership. There is only yearly data for the UK and it has a large margin of error. In other countries there is much less data.
  • I wouldn’t know how recommending alternative snakes could be done effectively. It may also be difficult to do without sending a message that it’s ok to own pet snakes. And yes, I am similarly extremely uncertain about whether that would be an improvement.
  • One day I’d like to look into changing agricultural practices to protect field mice, it does seem to be an important topic. However, it’s not in immediate RP plans.

Glad you liked the post :)

comment by Aaron Gertler (aarongertler) · 2019-02-21T01:37:36.024Z · EA(p) · GW(p)

Edited my reply to reflect the correct organization, thanks!

comment by saulius · 2019-02-21T12:51:54.732Z · EA(p) · GW(p)

ok, but I will leave my comment as it is because it seems that many people conflate RP and CE, and maybe some of them will see my comment :)

comment by kbog · 2019-02-21T19:09:13.242Z · EA(p) · GW(p)

There is quite a bit of recent controversy about pitbulls, that seems like the right place to start.

comment by Denkenberger · 2019-02-22T07:40:37.690Z · EA(p) · GW(p)

I would think the protein substitutes would be a lot cheaper than farmed mice - is that correct? Then it seems like that could substitute for a lot of the non "spectacle of eating live animals" market.

comment by Jemma · 2019-02-21T11:28:11.120Z · EA(p) · GW(p)

Interesting research. I first became aware of this issue from being involved in the animal welfare movement, specifically with small/"pocket" pets where sale of breeding "overstock" for reptile consumption is sadly common. Unfortunately, some people simply enjoy the spectacle of their pet consuming live prey. More generally, it's part of the broader issue of carnivore pets in general -- the meat produced for consumption by dogs and cats is likely to come from factory farms similar to those raising meat for human consumption, where conditions may be little better than those of the mice pictured here. This has led me to a personal decision to refrain from having non-vegetarian pets, and I know that other EAs have done likewise.

comment by saulius · 2019-02-21T12:46:59.696Z · EA(p) · GW(p)

It seems that meat produced for consumption by dogs and cats normally comes from the very same factory farms that produce human food. Because Animals claims that


Pet foods are made from both 4-D meat (animals that are dead, dying, diseased or disabled), and the leftover bits—referred to on pet food labels as “meat by-products”—of slaughtered farm animals. These parts include the snouts, udders, lungs, feet, organs, ears and other parts that humans don’t want to consume.

Of course, this doesn’t change much. Pet food allows meat industry to be more profitable, which leads to them farming more animals. I agree that this is a strong consideration against having carnivorous pets. There was a discussion about it in the EA forum here [EA · GW].

comment by saulius · 2019-02-21T13:07:58.507Z · EA(p) · GW(p)

I wonder if outreach to not buy dogs and cats could be more effective for reducing the number of farmed animals than vegan advocacy. And if corporate campaigns that encourage dog and cat food manufacturers to use higher welfare animals (e.g. gestation-crate-free pigs, broilers that are stocked less densely) could be effective.

comment by Peter_Hurford · 2019-02-21T16:05:39.265Z · EA(p) · GW(p)

This is definitely an interesting idea (two interesting ideas, I guess) worth exploring more. I worry though that some issues that might hold up these ideas are (1) these things generally being harder to compare, (2) not having any knock-on / flow-through effects of encouraging better behavior toward animals more specifically, and (3) companion animals being an important influence for people going veg.

Let me know if you'd want to look into this. :)

comment by ishi · 2019-03-08T02:02:18.911Z · EA(p) · GW(p)

I am against pet stores--there are at least 5 kinds of wild snakes snakes around here (copperheads, water snakes, green snakes, ringnecks, worm snakes, black rat snakes, black racers, maybe hognose snakes). i have mice right in my apt--i leave them alone. In another place i sometimes stay, there are corn snakes who live right out front, and rattlesnakes 100 feet away. I just look at them.