"Tagging will Tell" for 2024 Migration
From the August 20, 2024 Blog Post by Chip Taylor, Monarch Watch
Rainfall, if it persists for days – and it did over wide areas – can make a difference by limiting the number of hours and days during which females can lay eggs. In other words, it can reduce realized fecundity because there are only so many days in a female’s life and there is no way to fully recover from time lost. This idea is covered in a paper by Zalucki and Rochester (2004). The overall effect of delayed and reduced oviposition in June would be a reduction in the number of second-generation adults that emerge in July, and that, in turn, could result in a reduction of the number of offspring that become third and fourth generation migrants in August and September...
As most of you know, the size of the last generation is a function of the number of eggs laid from about 20 July to 5-10 August as well as the quality of the milkweeds and the weather. The adults from that oviposition typically emerge throughout August into early September. This year the emergence could be delayed due to a cold front that moved into the northern breeding area starting on the 4th of August. Overnight temperatures dipped into the 50s in many areas limiting the number of hours for larval development. It’s possible that development has been pushed back by at least 10 days. This means that monarchs that would normally be on the wing in early to mid-August are still larvae or pupae at this writing (19 August). Hopefully, that’s the case, and we are simply dealing with a late emergence and migration.
Stay tuned!
Please see the Monarch Watch Blog for the complete blog post from August 20.
Species Status Assessment and the three r’s
By Chip Taylor, Director, Monarch Watch
October 2023
When species are being considered for listing under the Endangered Species Act (ESA) by the Fish and Wildlife Service (FWS), a Species Status Assessment (SSA) is usually prepared. This assessment is based on the available science, and in some cases, the opinions of scientists that work closely with that species. At the core of the assessment are the three r’s: resilience, redundancy and representation. Resilience refers to data that may or may not support the ability of the species to respond to stochastic (random) events. Redundancy represents an assessment of the ability of a species to respond to catastrophic mortality. Representation seems to have two interpretations, the ability of a species to adapt to long term changes in the environment and/or the species role in the ecological processes in the range it occupies...
The silent partner in the push to have monarchs regulated is their cultural value. They are an iconic species. Their migration is remarkable. They are a species of wonder with a remarkable capacity to traverse a continent. Their beauty, and accessibility, along with charisma, generate emotional responses like no other insect. They are part of our heritage and reminders that we are the stewards of their fate being that we dominate the landscape and how it is used or misused. Biologically, they are an extraordinary example of the drive to survive and reproduce. Much remains unknown of how they respond to the physical cues in the environment and how those cues are processed in a manner that leads to behavioral responses. They are a model species for this research area. None of these considerations can be part of the SSA, yet they heighten the concerns about the need to sustain the monarch migration.
Read the full article here.
IUCN Changes Migratory Monarch Status from Endangered to Vulnerable
December 11, 2023
On December 30, 2021, the International Union for the Conservation of Nature (IUCN) added the migratory monarch butterfly (Danaus plexippus) to the Red List of Threatened Species as endangered. In June 2023, the IUCN Standards and Petitions Committee received a petition regarding their listing of the migratory monarch butterfly. The petition challenged the appropriateness of population models used in its assessment over the past ten years. After much deliberation, the Standards and Petitions Committee announced on September 27, 2023, that the IUCN would change their listing of the migratory monarch butterfly from endangered to vulnerable on December 11, 2023.
The primary reason for the shift in status was not due to a change in the current status of migratory monarchs. Many methods exist for examining population trends over time, all of which are complex, especially for a migratory insect with a broad geographic range. IUCN-specified criteria are based on the level of population reduction over the past 10 years or three generations, whichever is longer. In the original review, population data demonstrated a long-term population decline in migratory monarchs over multiple decades. When re-evaluated per IUCN criteria, the population decline within the last 10 years did not match the decline of the longer-term trend. Therefore the review warranted a change in IUCN status to be congruent with its evaluation criteria. Both methods of population evaluation used were scientifically valid. The monarch's IUCN status change highlights science's dynamic nature and the imperative need for continuous data collection and evaluation.
Read the full article here. |
