It’s definitely correct that rats do not consume their entire daily liquid needs from contrapest in field conditions. I can’t quickly find evidence for the 1.8L figure—this study includes a DC trial, but might not be the same one (the citation links in the EA Forum post weren’t working for me). Based on figure 9, 0 to 1200 mL of bait per month were consumed, depending on site and month. That’s not a good indicator of the effective dose, since treated adult rats might still consume some of it, but it could be a reasonable indicator of how much bait you’d need to buy to treat a given alley—although for the study I link, that’s complicated by the fact that I wouldn’t take their reports of reductions particularly seriously. Issues include: camera traps have to be used quite carefully to be good estimates of population abundance, and pairing them with a bait station is not good for that; it’s hard to tell whether rats are adults or juveniles once they’ve left the burrow and especially using camera traps; there’s no control sites, there were only two treatment sites, the treatment sites varied considerably in their features, etc.
Thanks for starting this thread, Lorenzo. I strongly upvoted your initial comment because it prompted me to significantly update the post. Thanks for the relevant context, Mal. I am now using the amount of rodenticide and fertility control bait for full depopulation per initial rodent instead of the amount needed to kill one rodent, and prevent one rodent birth. I think my current approach is better because full depopulation (in a given area) is the practical goal of using rodenticide or fertility control bait. In my past approach, the goal was preventing one rodent birth via fertility control for each rodent that would be killed with rodenticide, which I worry has little connection with the practical implementation of the intervention.
The conclusions of the post have not changed. I had calculated an increase in cropland of 0.621 m2-year per rodent birth prevented. Now I estimate a decrease in cropland of 0.413 m2-year per initial rodent. So the change in the living time of soil animals per initial rodent is −66.5 % (= −0.413/0.621) that I had obtained per rodent birth prevented. However, my conclusions only depended (and depend) on the ratio between the (size of the) effects on soil animals and rodents. As I said (and say) in the post, “I have very little idea about whether it [controlling the fertility of rodents instead of killing them] increases or decreases the welfare of soil animals”.
It’s definitely correct that rats do not consume their entire daily liquid needs from contrapest in field conditions. I can’t quickly find evidence for the 1.8L figure—this study includes a DC trial, but might not be the same one (the citation links in the EA Forum post weren’t working for me). Based on figure 9, 0 to 1200 mL of bait per month were consumed, depending on site and month. That’s not a good indicator of the effective dose, since treated adult rats might still consume some of it, but it could be a reasonable indicator of how much bait you’d need to buy to treat a given alley—although for the study I link, that’s complicated by the fact that I wouldn’t take their reports of reductions particularly seriously. Issues include: camera traps have to be used quite carefully to be good estimates of population abundance, and pairing them with a bait station is not good for that; it’s hard to tell whether rats are adults or juveniles once they’ve left the burrow and especially using camera traps; there’s no control sites, there were only two treatment sites, the treatment sites varied considerably in their features, etc.
Thank you! Here’s a link from web.archive.org of the EA Forum citation https://web.archive.org/web/20230715000000*/https://cdn.shopify.com/s/files/1/0255/4986/5032/files/DC-CASE-STUDY_NEW-BRAND_WEB2.pdf?v=1653689936
But yeah if we can’t trust that there was a real significant population reduction it doesn’t mean much
Thanks for starting this thread, Lorenzo. I strongly upvoted your initial comment because it prompted me to significantly update the post. Thanks for the relevant context, Mal. I am now using the amount of rodenticide and fertility control bait for full depopulation per initial rodent instead of the amount needed to kill one rodent, and prevent one rodent birth. I think my current approach is better because full depopulation (in a given area) is the practical goal of using rodenticide or fertility control bait. In my past approach, the goal was preventing one rodent birth via fertility control for each rodent that would be killed with rodenticide, which I worry has little connection with the practical implementation of the intervention.
The conclusions of the post have not changed. I had calculated an increase in cropland of 0.621 m2-year per rodent birth prevented. Now I estimate a decrease in cropland of 0.413 m2-year per initial rodent. So the change in the living time of soil animals per initial rodent is −66.5 % (= −0.413/0.621) that I had obtained per rodent birth prevented. However, my conclusions only depended (and depend) on the ratio between the (size of the) effects on soil animals and rodents. As I said (and say) in the post, “I have very little idea about whether it [controlling the fertility of rodents instead of killing them] increases or decreases the welfare of soil animals”.