SVG animation on path like the snail

Question

I have the following SVG and I would like to draw the circles pixel by pixel on the path after moveing. It's like when the snail goes he let a streak behind him. So my question is how to draw the light red circles?

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" viewBox="0 0 1000 200" id="svgBox" style="background-color:#e4e4e4">
    <path d="M3.858,58.607 c16.784-5.985,33.921-10.518,51.695-12.99c50.522-7.028,101.982,0.51,151.892,8.283c17.83,2.777,35.632,5.711,53.437,8.628 c51.69,8.469,103.241,11.438,155.3,3.794c53.714-7.887,106.383-20.968,159.374-32.228c11.166-2.373,27.644-7.155,39.231-4.449L10,10" stroke="grey" stroke-width="1" fill="none" id="animateMotion"/>
    <circle cx="" cy="" r="5" fill="red">
        <animateMotion dur="6s" repeatCount="0">
            <mpath xlink:href="#animateMotion"/>
        </animateMotion>
    </circle>
</svg>

Answer 1

You can do something like this for an instance:

.path {
  stroke-dasharray: 1230;
  stroke-dashoffset: 1230;
  animation: snail 6s linear forwards;
}

@keyframes snail {
  to {
    stroke-dashoffset: 0;
  }
}

    <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" viewBox="0 0 1000 200" id="svgBox" style="background-color:#e4e4e4">
        <path class="path" d="M3.858,58.607 c16.784-5.985,33.921-10.518,51.695-12.99c50.522-7.028,101.982,0.51,151.892,8.283c17.83,2.777,35.632,5.711,53.437,8.628 c51.69,8.469,103.241,11.438,155.3,3.794c53.714-7.887,106.383-20.968,159.374-32.228c11.166-2.373,27.644-7.155,39.231-4.449L10,10" stroke="pink" stroke-width="12" fill="none" id="animateMotion"/>
        <circle cx="" cy="" r="5" fill="red">
            <animateMotion dur="6s" repeatCount="0">
                <mpath xlink:href="#animateMotion"/>
            </animateMotion>
        </circle>
    </svg>

Answer 2

Maybe this article which I think will give you some pointers, and its linked example CodePen here. I cut & pasted your path and set the id and the line gets drawn as per your 'snail trail' requirement.

Here is the resulting svg:

<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
     width="340px" height="333px" viewBox="0 0 340 333" enable-background="new 0 0 340 333" xml:space="preserve">

      <path class="path" d="M3.858,58.607 c16.784-5.985,33.921-10.518,51.695-12.99c50.522-7.028,101.982,0.51,151.892,8.283c17.83,2.777,35.632,5.711,53.437,8.628 c51.69,8.469,103.241,11.438,155.3,3.794c53.714-7.887,106.383-20.968,159.374-32.228c11.166-2.373,27.644-7.155,39.231-4.449L10,10" stroke="Orange" stroke-width="10" fill="#FFFFFF" stroke-miterlimit="10" id="animateMotion"/>

  <path class="path" fill="#FFFFFF" stroke="#000000" stroke-width="4" stroke-miterlimit="10" d="M66.039,133.545c0,0-21-57,18-67s49-4,65,8
    s30,41,53,27s66,4,58,32s-5,44,18,57s22,46,0,45s-54-40-68-16s-40,88-83,48s11-61-11-80s-79-7-70-41
    C46.039,146.545,53.039,128.545,66.039,133.545z"/>

</svg>

And the CSS

.path {
  stroke-dasharray: 1000;
  stroke-dashoffset: 1000;
  animation: dash 5s linear alternate infinite;
}

@keyframes dash {
  from {
    stroke-dashoffset: 1000;
  }
  to {
    stroke-dashoffset: 0;
  }
}