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The overwintering monarch population in Mexico was the lowest (2.83 hectares) yet recorded by Eligio Garcia for all overwintering colonies combined. If we use the number of monarchs per hectare suggested by Bill Calvert at the recent meeting in Lawrence (10 million) this means the overwintering population numbered roughly 28 million. Given that approximately half of the monarchs die during the winter and many more die on the way north before they have an opportunity to lay eggs, the number of female monarchs entering the US in March may have been in the range of 5-6 million.
The question is: Is this a sufficient number of females to result in a recovery of the population to normal levels (roughly 60 million) this breeding season? The answer is: Maybe! It depends on how successful the monarchs are in reproducing over the next three months.
Fortunately, even though the arrival of the monarchs was delayed in Texas and throughout the country, the rains of the previous fall, winter and early spring in Texas provided excellent conditions for milkweed and nectar resources for the breeding monarchs. Each year the key to the rest of the season often seems to be the reproductive success of the first generation. This year the reproduction seems to have been better than usual. Good numbers of monarchs have been seen moving northward through eastern Kansas since mid May and this movement has continued into June. More importantly monarchs arrived in the northern states in mid May and good numbers of eggs have been reported in a number of locations. At this point, the prospects are good for a fall population that will be larger than that of the drought-plagued 2000 season.