CR Voles please help! The prairie vole, a small North...

[RonPurewal]

Thanks Ron, understood.

It seems like a little bit of a hairline difference and tricky, given that the seasons in question (winter and spring) occur in close succession.

With all due respect, I don't think this is true at all. The difference is huge. In fact, it is the largest possible difference: we're talking about literally opposite points on the calendar.

If this is not clear, then think about specific months. Say we define "winter" as December through March, and "autumn" as September through November.
Then the passage says...
Voles commonly live in large groups from November through March; from April through September, however, most voles live in far smaller groups

"Smaller groups from April to September" very clearly rules out "harsh winters" as a cause of mortality!

[RonPurewal]

Isn't it plausible that when the winters are harsh, the effects of the diminishing population may only be noticeable a little later, say at the onset of spring?

In this context, no.
If "temperatures [that] drop well below freezing" are a cause of mortality in animals... that means the animals freeze to death.
That happens immediately"”within hours, at most. Doesn't take months.

[RonPurewal]

It could work the other way as you mentioned - the population could finally begin to show signs of recovery post the harsh winters.

The passage states that the population stays small all the way until the subequent early autumn"”like the following September. All the way through the spring and summer months. That doesn't square with this idea.

(Also, don't forget the whole "freezing is instant" thing, as mentioned above.)

[nicolette.omoile]

Hi Ron,

I just want to make sure I understand the plural / singular noun situation (I choose B).

a variety of approaches...

I considered a "variety" to be the subject -- so I disregarded the prepositional phrase "of approaches" and made the verb match with variety.

Can you clarify for me the rule of when the number in the object of a preposition DOES influence the singularity / plurality of the subject and when it does not? Thanks!

Nicole

[xmjzeng]

The stated facts"”that the population stays large through the winter and experiences a diminution through spring and summer"”don't square with that.
In fact, those facts are exactly the opposite of what we would expect to see: the population plummets as winter turns to spring"”exactly when it should start to increase again!

Ron -- when reading the question, I was under the impression that "voles commonly live in large groups from late autumn through winter" and "live in far smaller groups" from spring through early autumn mean, respectively, that the groups in which voles live have more members in late-Fall/Winter ("F/W") than members in Spring/early-Fall ("S/F"). The total population of voles may still be the same, e.g. total population = 100, but in F/W, there are 4 groups, with 25 voles per group; in S/F, total population still = 100, but there are 10 groups, with 10 voles per group.

Explanation for this phenomenon could be due to the temperature -- more voles living in a community means more body heat and higher chances of survival in young moles. In the spring, temperatures rise, and there is no longer a need for such large groups. Is this extending the assumption too much?

I'm having a hard time seeing how the predatory activities of snakes cause group size of the voles to change, if group size does not refer to population size. Are the two synonymous in this question because the last sentence says that the seasonal variation in group size is probably explained by seasonal variation in mortality?

Thank you!

[RonPurewal]

Are the two synonymous in this question because the last sentence says that the seasonal variation in group size is probably explained by seasonal variation in mortality?

Thank you!

Yes, exactly.

The passages will not draw conclusions that are complete nonsense.
If the author invokes variations in mortality as a possible explanation for something, then we're talking about ... well, mortality. Death.